This is a bit strange and silly.  You are married and that's a fact, regardless of what country you were married in if the marriage was legal and valid at the time it was entered into.  FOreign marriages are granted full faith and credit in the US so there is no need to get remarried.  In fact you really cannot be remarried if you are already married.  So, cutting ties with a country means more like surrendering any citizenships, etc.  No matter what happens with a country, marriages entered into previously are still considered marriages, both there and in the US.  I would say you do not need to do anything extra.  Now, if you want to re new your vows in the US, you can do that, but it's more for symbolic reasons.