This is part of the reason why increasing federalization and consolidation of governments of the world worries me. A big part of progress in society is a crapshoot and arguably a lot of what we do is inadvertently harmful to society. Allowing experimentation in relatively small segments of the population compartmentalizes risk while allowing everyone else to copy it if they see it works.
How much copying is actually happening? I live in the US, and our healthcare system is objectively terrible. There are numerous examples of systems in other countries that provide better care for more people for less, but we refuse to adopt any of them.
First past the post voting is also obviously terrible, and many better ways are available and have had successful implementation, but nothing changes here.
Theoretically what you're saying makes sense, but it doesn't seem to match reality. Instead we just get a lot of tribalism, war, and death.
Perhaps it is more of a question on scalability. It is often claimed that Taiwan has a universal healthcare system in place (sustainability is often challenged) in which cannot be replicated in the US due to demographic and geographic factors let alone political ones.
Experimenting with health care systems at the state level would be a perfect example where more experimentation at scales smaller than the national level would be very helpful.
