Re: American citizenship and second wife.
He’s probably as willing to marry a second wife for reasons we can all imagine 
and blaming his sister’s situation. If he were man enough, he would get out of it.
The wife in US should figure out the best way to handle this by first contacting a social worker.
Re: American citizenship and second wife.
Umm how do we know the man isn't just lying to get a sob story or something?
Anyways, the guys sisters relationship with her in laws is of no relevance to the woman in this situation, she needs to do what she can to get her life back on track. if she wants to spend the rest of her life funding someone's drug addiction....well good for her then.
I agree. If not now she might have to file for a divorce a few years from now.