Registering to vote is pretty normal. You might not have to because the government already has records of you and that is the same in America for a lot of people. For immigrants in Europe you still have to register!
If you change municipality or state in Europe you might also have to register again so they have you voting in the right local elections.
The original cities skylines had atrocious performance after a certain city size as well, especially on hardware available at launch. Hopefully they can deliver on better performance over the next few months, I expect it to improve before they do their console release.