Can a bank account in Mexico be garnisheed for a debt.

If they can find it, it can probably be garnished, did you have to use your social security number to open it, if so, then yes.

Yes, while it is harder, they would have to file in Mexico court a request fot he US order to be honored, there is trade agreemetns in place to allow the garnishment to happen.

If it's a Mexican debt, probably. If it's an American debt, then your answer is only with the cooperation of the Mexican authorities. How far out of their way they'll go to help an American collect on a debt that is of American origin is anybody's guess but my hunch is that they won't want to be bothered.