I don't think it's that America can't enforce sanctions, it's that sanctions don't work against countries with valuable resources (because everyone else wants t

I don't think it's that America can't enforce sanctions, it's that sanctions don't work against countries with valuable resources (because everyone else wants to buy them), or against many countries at once (because you've just created an alternative trading bloc), or against very populous countries (because companies will go far out of their way to be able to access large markets).