At the time of your marriage did you know that the girl was already married to another man?
If you did not know nothing would happen to you. But if you know Section 497 of IPC says:
Whoever has s*xual intercourse with a person who is or whom he knows or has reason to believe to be the wife of another another man, without the consent or connivance of that man, ------------------ is guilty of an offence of adultery. Punishment is 5 years' imprisonment, fine or both. There is no punishment for the wife.
But as soon as you came to know that she was wife of another man, you should desist from having s*xual intercourse with her with proof for the same. Your marriage also would be null and void.
In any case you wife will be punishable under Section 17 of Hindu Marriage and Divorce Act, 1955 and under IPC 494 and 495. Under 494 she can get up to 7 years' imprisonment. If she had concealed the first marriage from you she can get up to 10 years under Section 495. If Sections 495 and 497 are put together only one of you can be punished under one of the two Sections.
These are laws of India. I do not know about US laws.