Sure they would. Other nations charge tariffs on our goods all the time. Some even ban some of our products from their countries. Tariffs are no different than fines.
What are they going to do if we don't pay the fine? The worse they could do is put us back to where we were before any agreement.
When trade was unilateral, it was nation to nation. Because the WTO makes trade multilateral, it is one nation, us, against many.
If we don't pay the fines, which are not tariffs btw, they can conduct a multilateral campaign against us. It puts US citizens in a very bad position, whether you say we have to pay the fines or not. It only makes ammunition for the other nations of the world and it doesn't have to be that way. But you see the internationalists who put America in that position, like it, because we're damned if we do and damned if we don't.
Why would a loyal government put their nation into that situtation?