Question

Could the American federal system survive without the supremacy clause?

Answer 1

It's a good question. In my opinion, in the long run, probably not and was one of the reasons why the Articles of Confederation were replaced. The supremacy clause provides for the Constitution and the federal laws derived from it as "the law of the land" superseding any local laws (as long as federal laws are not unconstitutional). It's kind of like saying that there has to be someone in the room to lead the debate and make the decisions.

The idea is that without a unifying voice can cut across state lines and local jurisdictions, the idea of a Union would be much harder to maintain. Every state could conceivably start building up laws without respect to the Constitution by pursuing their own interests focused on themselves instead of the nation. One state could enact Prohibition all over again, another could make its own trade laws, another could go off and negotiate with the international community on its own and create treaties, etc..