Check your state party registration rules. Made the same mistake in my state when I switched from Democrat to Republican in 2016 when I wanted to vote in the primaries. In my CT, Republican party requires registration something like 6 months before an election. I think for Democrats it's like same day or shortly before the election is allowed. Different party rules, makes no sense to me why they do it that way, but could just be how the Republican party created their party registration rules in Utah.
Fellow CT anon. Depends where you are. CT is largely rural. Outside of Southern Fairfield County where our asshole governor comes from and cities like Bridgeport, Waterbury, New Haven and Hartford, I see more Trump signs. Own and run a business in Fairfield county. There are a ton of liberal rich assholes that move here from NY, but I think most CT folk are quietly conservative and independent (based on interactions with clients). The libtards are usually rich outsiders and indoctrinated teachers/students.