What works well in one state in the US that does not in another?

I’m referring to policies, programs, mandates, that sort of thing. What made me think of asking the question was another Q pointing out how Romney was for Romneycare but not for Obamacare. Romney says it is good for Massachusettes, but not for every state. So, I was wondering, where has this sort of thinking proven to be true? Don’t limit this to just healthcare; think education, labor protections, anything you can think of. I’m looking for examples where a program worked amazingly well in one state, and then when brought to another it failed; did not get the desired result.