2) I think you overestimate the involvement of the US federal government in law-enforcement across the country. A lot of (most?) laws are actually passed and enforced at state level, with the FBI only getting involved in the worst situations or where cross-state cooperation is necessary. California alone has tons of gdpr-like laws that it sets and enforces independently. There is an entire US political culture based around "state rights" that constantly pushes for having a looser federal structure that looks very much like what the EU is today.
3) it's not like they don't have universities in Minnesota or Nebraska, a lot of people sticks around where they were born. The difference is that the ones who don't, find it easy enough to relocate. This helps creating world-beating industrial districts like Hollywood, SF, Houston, New York, etc etc - because they can attract the best of the best among 400m people.
100 years ago people rarely moved from a village. 50 years ago they rarely moved from a city. Now they rarely move from a country. See where it's going?