If the foreign spouse has already become a U.S. citizen, then it should have no effect.
If a temporary resident card has been issued, but the permanent resident card (green card) has not yet been issued, a divorce might lead to the spouse being removed, unless they have other grounds to remain (such as a VAWA application).
If the green card has been issued but the citizenship interview has not yet taken place, there can be some difficulties and delays.
If immigration is an issue in your case, we would need to proceed strategically.
If there has been fraud in the immigration process, then the matter requires careful analysis beyond what should be discussed on a website.