Should the dowry paid to a mentally ill wife be reconsidered after the discovery of alleged deception, and what should be done regarding potential claims under US law in the event of divorce?

The matter should be referred to the Sharia (definition) judge. If there is no judge, the woman is entitled to the dower (sadaq) in consideration of what the man has made lawful from her private parts. As for the wife's illness, if it prevents or causes aversion to enjoyment, the man has the right to reclaim what he paid from whoever deceived him. However, if he was not deceived, he has no right, because he neglected to inquire.