For heavy users and given a standard range of 250+ miles, we are talking about a longevity of 1 000 000 miles. I never had a car with more than 200.000km (120 000 miles).
Also, there's just smog you need to pass which is significantly less than in many other developed countries. Some have yearly required checks that would check all safety features like brakes, tires etcetera. That's where a lot of cars fail that would just keep driving in the US
Outside of the rust belt, cars last quite awhile as long as you change oil and the occasional rubbery bit.
I'm actually scrapping a 99 Jeep TJ right now because the OEM powertrain is just awful, but the rest of the vehicle is perfectly fine.
That said, a million miles is probably enough for anyone :D