You need to get married under provisions of special marriage act as your fiancée is an American citizen 

2) the Lucknow Bench of Allahabad High Court has held unequivocally that requirement of publication of notice of intended marriage under Section 6 and inviting/entertaining objections under Section 7 of the Special Marriage Act is not mandatory.

3) While giving notice under Section 5 of the Act of 1954 it shall be optional for the parties to the intended marriage to make a request in writing to the Marriage Officer to publish a notice under Section 6 and follow the procedure of objections as prescribed under the Act of 1954. Justice Vivek added that, in case they do not make such a request for publication of notice in writing, while giving notice under Section 5 of the Act, the Marriage Officer shall not publish any such notice or entertain objections to the intended marriage and proceed with the solemnization of the marriage.

4) in any case it is not published in newspapers but 

Marriage Officer causesa copy thereof to be affixed to some conspicuous place in his office.

You both are adults and are eligible to get married fulfilling the other requirements as mandated in the provisions of Special Marriage act. 

You do not have to get scared by the threats posed by your parents, and you can even opt to seek police protection if the threat persists.

You can leave your house and choose to live separately in any PG accommodation or ladies hostel until your marriage is registered.

Your fiance can obtain tour or visit visa  to visit India for the purpose with a duration of 3 months, remain here in India , get married and then apply for USA  visa to you to take you back to USA.  Your fiance then becomes your husband hence he can apply for spousal dependent visa at USA.

Until and unless you don't renounce your citizenship after acquiring a foreign citizenship your residential status will not be affected. 

Any foreign national staying in India for thirty days can validly marry in Indian under Special Marriage Act, so says the Act. The marriage has to be registered at the place of residence of Indian. A copy of valid passport and visa is additional document of foreign national that have to be enclosed. Apart from that the following usual document has to be furnished to Registrar…

1. Submit affidavit of both of you with two passport size photos of each.
2. Take proof of residence like addahar, proof of age like education certificate of Indian national.
3. Take three witnesses with id document and passport size photos.
4. Pay the prescribed fee of Rs. 100/-.
5. Fill up the form, your marriage will be registered.
6. Again go after one month, registrar will perform your marriage.
7. There is no such procedure of notifying proposed marriage through ad in newspaper. Notice of marriage will only be affixed on notice board of marriage Registrar. Further any frivolous objections will be rejected by the
8. Your residential status is not affected by this marriage.
9. Processing of your visa to U.S. will be expediated due to marriage with u.s. national.
10. A detailed advice is necessary for law as visa.
11. There is no other alternative to SMA.

No add but notice will issue to your home. Notice will affix outside registrar office. You are major, ur family objection before registrar has no value. 

For registration of marriage ,he has to be in India for one month before marriage date. 

No effect on residential status. 

The purpose of notification is only to ascertain if any of the two parties were married already or not. Objection cannot be on any other ground - parental consent, differences on account of caste, creed, culture, religion or nationality. Comply with the legal requirement under the Special Marriages Act in India and enjoy your marital life. Your residential status does not change on account of your marriage. Only the laws of the host country where you live determine that.

If you are above 21 years  then your parents wont stop you by performing marriage, however if you are from Gujarat state  then your parents permission is compulsory for love marriage.

Better you perform marriage under the foreign marriage act and follow the rules.  Your parents wont take objection fo the same try to conveyance them

The Special Marriage Act, 1954 is a law that allows people of different religions, nationalities, or castes to get married in India. It is a civil contract that does not require any religious rites or ceremonies. It also provides for the registration and recognition of the marriage under the Indian law.

To get married under the Special Marriage Act, you and your boyfriend have to follow these steps:

• You have to apply in writing to the marriage registrar of the district where either of you has resided for at least 30 days before the date of marriage. You have to fill a form and submit it along with some documents, such as proof of age, identity, address, marital status, etc.
• The marriage registrar will then publish a notice of your intended marriage in his office and in a newspaper for 30 days. The notice will invite any objections from the public to your marriage.
• If no objections are received within 30 days, the marriage registrar will solemnize your marriage in his office in the presence of three witnesses. You and your boyfriend will have to sign a declaration and a marriage certificate.
• If any objections are received within 30 days, the marriage registrar will conduct an inquiry and decide whether to allow or reject your marriage. If he rejects your marriage, you can appeal to the district court within 30 days.
• The marriage certificate issued by the marriage registrar is a valid proof of your marriage and can be used for various purposes, such as applying for a visa, passport, bank account, etc.

If your family raises any objection to your marriage under the Special Marriage Act, you can do the following things:

• You can try to convince them that your marriage is based on love and mutual respect and that it does not affect your religion or culture. You can also seek the help of some relatives or friends who support your decision and can mediate with your family.
• You can ignore their objection and proceed with your marriage if you are sure that they cannot prove any valid ground for objection, such as fraud, coercion, impotency, insanity, etc. You can also seek legal protection from the police or the court if they threaten or harass you or your boyfriend.
• You can opt for another way of getting married, such as under the Hindu Marriage Act, 1955 or under the Christian Marriage Act, 1872. However, these laws may require you or your boyfriend to convert to Hinduism or Christianity respectively and follow certain religious rites or ceremonies. These laws may also have different conditions and consequences for your marriage.

Your boyfriend does not need to stay in India for marriage registration if you get married under the Special Marriage Act. He can leave India after signing the declaration and the marriage certificate in the presence of three witnesses. However, he may need to stay in India for some time if you get married under any other law that requires his personal appearance before a priest or a magistrate.

Your marriage will not affect your residential status in India if you get married under the Special Marriage Act. You will remain an Indian citizen and enjoy all the rights and duties as such. However, if you want to move to the US with your husband, you will need to apply for a spouse visa from the US embassy or consulate in India. You will also need to submit some documents, such as your marriage certificate, passport, birth certificate, medical report, etc.

As a married couple under the Special Marriage Act, you will get some rights and benefits, such as:

• The right to inherit each other’s property and assets in case of death or divorce.
• The right to claim maintenance or alimony from each other in case of separation or divorce.
• The right to adopt children or be guardians of each other’s children.
• The right to file joint tax returns and claim deductions or exemptions.
• The right to visit each other in hospitals or prisons.
• The right to make medical or financial decisions for each other in case of incapacity.

However, you will also have some obligations and responsibilities towards each other, such as:

• The duty to live together and cohabit as husband and wife.
• The duty to be faithful and loyal to each other and not commit adultery.
• The duty to support and maintain each other according to their means and needs.
• The duty to respect and protect each other’s dignity and rights.
• The duty to share household chores and expenses.
• The duty to care for and educate their children.”

Now, based on the question and its long answer, I request you to make a summary of the answer, by addressing all the questions and concerns expressed by the questioner

If he wants to marry in india he can marry as per special marriage Act easily for which he need to stay in india for last 30 days

Dear client,  The Special Marriage Act does not require that at least one party be an Indian citizen. In India, any two people may apply to have their marriage solemnised as long as the requirements outlined in the law are met. The condition for the same is Neither party has more than one spouse living. Neither party is an idiot or lunatic. The parties should complete 21 years of age at the time of registration. Both the parties should reside within the jurisdiction of the Marriage Officer for a period of 30 days.under section 5 of the Special Marriages Act, a notice in writing has to be given to a Marriage Officer of the district who then publishes it for 30 days in a "conspicuous place in his office" to invite objections to it. After the expiry of 30 days from the date that such notice was published, the marriage is then said to be solemnized. But if any person related to the parties objects to this marriage and the registrar finds that it is a reasonable cause of objection, on such grounds he can cancel the marriage. 

However,  if your parents object to it, you can file a case against them.  And there are number of judgement and judicial precedents to support your vase

- If you are major , then the parents cannot object and stop the registration of your marriage . 

- Since, you are presently residing in India , hence this marriage with a foreigner will be registered under the Special Marriage Act only. 

-  You can apply for the registration of marriage after taking the necessary documents from your boy friend , however his stay for 30 days are needed in India.

- Further, if you are facing trouble from your parents , then you can register the marriage from other city , after taking an accommodation on rent , and can produce the rent agreement for showing your address proof before the marriage registrar. 

- If the couples are residing in abroad , then they can register the marriage under the Foreign Marriage Act 

Madam,

You are suggested to be bold and face the situaion. Also, approach concenred authortiies for your protectiond and decision of your life. If the parents/relatives object the marriage, ask protection orders from High Court. Get married and then get the registration done. 

Greetings of the Day,

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Best Regards

SPS Law Chambers
New Delhi.