> People could pick and choose where to move depending on what they like.
People may be legally free to move between states, but certainly very many are not economically free to move between states.
> There is no political experimentation anymore
There certainly is significant political variation between the states, with some of those single-state variants becoming popular and spreading.
There may not be changes in the direction you want or on the issues you care about -- but that's different than an absence of political experimentation.
What you say is technically true, but kind of misses the point. Historically variation between the states was so great that today's variation is practically indecernable. Political experimentation still exists, but is difficult, because of strong centralized government. A strong centralized government makes some experimentation impossible and other experimentation gets pushed to the federal level even if not appropriate to the nation at large.
People may be legally free to move between states, but certainly very many are not economically free to move between states.
> There is no political experimentation anymore
There certainly is significant political variation between the states, with some of those single-state variants becoming popular and spreading.
There may not be changes in the direction you want or on the issues you care about -- but that's different than an absence of political experimentation.