Compared to moving to another country? Yes it absolutely is. There are no legal impediments for moving to and living/working in another state for a US citizen. This in contrast to even the EU, where despite freedom of movement, there are significant legal restrictions/requirments depending on state/jurisdiction for permanent alien residency.

The only real impediment to moving between states as a US citizen is financial and social, but this is the case literally everywhere, even intrastate.

Because it is...? People move to different states all the time just to change jobs.

If you disagree with the way that your state operates so strongly that you can't stand it anymore...moving becomes a pretty easy decision.

You absolutely do not have that freedom. Every country has their own rules and has it in their power to prevent you from moving to their country permanently.