Since I started playing tennis I haven't moved, but I have played players who have moved here from different parts of the country. I have not noticed any huge discrepancies in level of play for a particular level. In fact I have noticed that players from the supposedly strong tennis states- CA, FL and TX did not do as well after they moved here based on their prior USTA record. OTOH we have had some players from the mid west that were not from traditional strong tennis states- like OH and Indiana that have been top level players here at the same level.
I think this does vary by level even within the state. For example here 3.0 level participation is pretty weak on both mens and womens side so most play at 3.5. The mens USTA 4.5 is basically dead because a very popular alternative league that has all the 4.5-5.0 players. The 4.0 level though is pretty strong as a result since above that level there is not much going on as far as USTA so there is a lot of incentive to keep players at 4.0 and a lot of high level players entering the system end up at 4.0 instead of 4.5