Here’s a theoretical puzzle to consider. States possess a certain degree of sovereignty in our federal system. Congress though, has the power to create a new state through ordinary legislation signed by the President. This could be read to mean that the Federal Government is the source of state sovereignty and that the states are merely delegated that authority as if they were administrative agencies.
But that can’t be right. The original 13 states were not created by Congress. Moreover, once a state is created it gets the same rights as the existing ones. This creates an anomaly that did come up in the 19th century. Congress could insist that a territory meet certain conditions to get statehood (Utah, for example, had to renounce polygamy). Once a state was admitted, however, it could do whatever it wanted. Now Congress could respond by declaring a state no longer republican, which would diminish, though not eliminate its sovereignty, but that’s never happened in the way that I’m describing. So I’m not sure how any pre-admission bargains were enforced. Makes me wonder if there’s a good article in just looking at all of the legislation admitting states since the Founding to see what I’d find.