I feel like for most of my life, people said "Nevada" with a wide /ɑː/, as in father, but for the last several years I consistently hear people say it with a short "a", as in apple

But... that's not right. In Spanish, "A" only makes one sound, and it's closer to /ɑː/ than /æ/. Sure, (n'-VAH-d') is still an English approximation (because we don't have a β sound) but it's a closer approximation than (n'-VA-d'). Why did everyone suddenly decide to say it less correctly?? We're not correcting a historical record, here. It's not like Nevada was named after a person who used an anglicized pronunciation, it's literally just the Spanish word for "snowy".

I'm not normally a prescriptivist about pronunciation, but I dunno, it seems disrespectful to not even make a token effort to acknowledge languages besides English. Maybe I can't do the trilled Rs and bilabial approximates, but I'm going to get as close as I can

If you're an individual and you want to pronounce a word differently than I think it should be I'm not going to correct you. But look, if a state or any other kind of business names themselves after a real word but pronounce it weird, I'm going to say the word the way that it's said. I have way more respect for languages spoken by real people than the brand guidelines of legal fictions 🦝