City limits are irrelevant, what matters is urban density. If you work 8 blocks from where you live, you're going to have a short commute regardless of whether people living 20 miles away are considered to be in the same administrative region.

19.63 km is the average commute distance in manhattan, one of America's densest cities and a place where most people don't even use cars. The average for america in general is 67.2 km. And those are averages for a daily use. People need cars that can handle the longest distances they would need to travel. People don't drive 500+km every day, but trips of that length are not unusual either. I'm going to be driving 650 km one way tomorrow.