There are some who worry that ethnic hostilities, unchecked immigration etc. within the United States will eventually cause the downfall of the nation, and they therefore call for the secession of states and regions, creating two or more countries. While I also see the coming ethnic civil disruptions, I think that the legal separation of powers and states in the U. S. Constitution could accommodate ethnopluralism in a less radical and conservative way. We can keep the nation and Constitution intact but adapt it to our unassimilating ethnic cultures. Although this probably would not happen quickly, we can give power back to the states in accord with the Tenth Amendment to the Constitution, which expresses the principle of federalism as the foundation plan of the original Constitution---that is, the federal government possesses only those powers delegated to it by the Constitution and remaining powers are reserved for the states or the people. It is fortunate that our Founding Fathers set up the separation of powers and states in the Constitution which could accommodate the saving grace of ethnopluralism---if we really wanted to do it, and have the wisdom to do so.
The conservative (and sometimes liberal ) movement of localism also affirms this natural legal separation. Here is a good interview from July in the American Conservative magazine which shows how localism prospers even in a age of globalization: "A World of Cities" by Alan Crawford.