where is the best place in U.S. to live with severe asthma

Hi jca, and welcome! I see you are a new member here, having joined today, just a few hours ago. We are glad to see you engaging already with the community through this, your first post.
We appreciate your post and question - it's a good one!
We actually have a number of articles, published right here on asthma.net, which speak to this issue. Should you want to look over the material, here is a link to several of those articles: https://asthma.net/search?s=best%20cities%20to%20live. When you have an opportunity, take a look at the first three articles - I think they may be of some interest for you.
Should you want to read something additional, our sister site, COPD.net, published this article, which also may give you some additional insight: https://copd.net/living/best-places-live. Even though it speaks to COPD, many of the triggers (for COPD) also apply to asthma.
I understand that your present thinking is that the climate and air quality in Houston may not agree with you. Where have you lived besides Texas? How was your asthma in other places you have lived?
Wishing you well,
Leon (site moderator asthma.net)