If you live in the states on the map below* with same-day voter registration, you can still vote even if you haven't yet registered to vote! (*early voting has ended in NC and NY)
Another note that New York is currently even weirder having only allowed same day voter registration on a single day of early voting rather than the entire period unlike North Carolina
Honestly, I can't believe you guys have to register to vote and can be denied if you forgot/couldn't when it's so different in Ontario/Canada. I can just walk in to a polling station, give them my driver's license, and go vote. Hell, you can even vote without ID (subject to certain requirements) if you need to.
No, there are some red, blue and swing states in there. It's kind of a weird mix of states because there a few blue states that don't have it and some red states that do