Which divorce law would apply Hindu law or American law?

As a general rule, United States courts will apply the law of their home jurisdiction in divorce matters unless there is a very compelling reason to use foreign law. I am aware of only two situations in which United States courts have applied foreign law to divorce matters: (1) where a divorce is obtained in the courts of a foreign country while property or children are present in the United States, and a United States court must decide whether to honor the foreign divorce decree with respect to the property or children, or (2) the spouses signed a prenuptial agreement and/or marriage contract that calls for foreign law to govern the divorce. Even if you can convince a United States judge that your divorce falls into one of those two situations and should be adjudicated according to foreign law, the judge will still retain authority to approve or reject the final distribution of property and award of child support. If the application of foreign law results in an outcome that does not comport with American principles of fairness and justice, the judge almost certainly will find a way to ensure that domestic United States law is applied.

The law that will apply is the law in the state in which you are a resident when you file for a divorce.

USA law applies, specifically the law of the state you file in.

American law

American law of the state the parties reside in.