It's very, very easy.
The last time I personally did license renewal, I waited approximately that long without an appointment, and the place had a line out the door.
Theoretically yes, but practically it's moot. Were I live I don't think I've ever had to wait in line more than 10-15 minutes, even at what seemed to be "busy times." If the wait times are that short, it's more trouble to make an appointment and still wait about that long.
That's nice for you. Every time I've gone to my local DMV I've waited at least 45 minutes, even with an appointment. Luckily I work remotely so I could work from the waiting area, but most people don't have that luxury and are forced to take an indefinite time off of work to go to the DMV.
That's not something you can generalize about in the US. Here, driver licensing is a state-level function, it's done >50 different ways. It's not even official done by the "DMV" everywhere, but that's what they call in in California, so that's what they call it on TV. Even in my state it's hard to generalize, since they allow contractors to perform almost all the common functions in their businesses.
Do you not have driving tests in Sweden? Does Sweden allow residents to submit any random picture of their choice for their drivers license?
As an American, the only times I have to go to the DMV are when I have renew my license (every 4-5 year), and that seems mainly to take a (simple) vision test and get my photo taken. They also give tests to new drivers and people moving in from out of state.