[crazygringo]

What are you talking about? Sure you can focus on the state level if you want instead of country-level, but there's still plenty of room for federal policy that supersedes state/local policy.

So it very much is how it works, but there are technical questions about how much and in which areas.

As for migration, I don't have the slightest idea what you're talking about. Most countries don't have a federal structure to begin with, including most democracies.