I am not an American. We don't have a DMV. Why the heck would vehicles and elections be organised in the same place? It takes actual time to register here (up to several months).

For most people, your main form of government issue ID is your drivers license. Since they're a government agency, and they have all your information, they let you register at the same time. Its actually pretty convenient, though the DMV itself is very slow and inconvenient.

Unless it's a general election people don't take that much notice, and it's hard to find out about one when people only talk about American elections online and you also aren't always in the country.

That's true. Most people only pay attention to the general. Even still, when there's a local election you'll almost always see political things around town, so if you care it's not hard to keep track of.