I doubt the U.S. would simply blow up stablecoins. (Unless e.g. the Kremlin is buying Iranian munitions with it and nobody does anything to stop it.) That said, coming regulation will likely require elements of KYC. That could result in enforcement actions or users in back-of-mind countries getting locked out.
All of which sidesteps dollar stablecoins relying on the dollar for their stability, not anything crypto.