I’ve actually had kind of the opposite problem: people disagreeing with an ID that I’ve made on an observation, because “you shouldn’t rule out X, because it occurs in Colorado too!”
Thing is, there’s this great big tourist attraction running down the middle of the state: the Rocky Mountains. (Maybe you’ve heard of them?) The average elevation of the Continental Divide is some 10,000’ / 3050m; the highest point (Grey’s Peak) is 14,270’ or just a hair under 4350m. That’s a pretty significant barrier.
I live on the Eastern side: the Front Range. Every time I’ve dealt with this sort of dissenting opinion, though (or usually not dealt with it, because I have no idea how to respond), what’s proposed is a species that occurs on the Western Slope, often in limited areas, without a single record east of the Divide in 60+ years.
I get that things show up in places where they were previously not supposed to be, and it’s just going to get more common. iNatters are documenting these changes and effectively redrawing range maps in real time. All that being said, you still have to take geography into account.