Not much to add about what's already been said, but I will mention that my 1998 Ford Mustang made it to 175,000 miles before I got rid of it in 2006. It was still technically running, but just needed some TLC. It had a habit of burning out cooling fans (an electrical problem) that aggravated me. Replacing them was only about $60-70 but I went through 3 in the last year that I owned it. It also needed a lot of "standard maintenance" - new shocks, new tires, new brake pads/shoes, battery was old, etc, so rather than do a complete overhaul I sold it cheap to a high school student. She had some friends work on it and AFAIK she's still driving it. Before that I had a 1993 Camaro that I got well past 100,000 (I think it was around 125,000) before I totaled it in an accident (I wasn't at fault). Not only were both of those American cars, but both were particular models that had a reputation for being mechanically troublesome.
My current car that replaced the Mustang is a Hyundai Tiburon (Korean ownership - not sure where it was actually made). So far so good on that one too - currently around 55,000 miles on it if I remember right. Aside from wiper blades, a fuse, and oil changes, all I've had to do so far is replace a battery that went bad. The backlighting on the shifter has also gone out, but that's pretty minor stuff.
While everyone makes a lemon every now and then (and on the flip side sometimes even the worst company will happen to turn out one item that just works better than the rest), and EVERYTHING will need some servicing somewhere between, I think a lot of it boils down to how hard people are on their cars. I've seen some people that will take a brand new car and just from the way they drive it it will be falling apart a year later, no matter who made it. One of my cousins when through 4 trucks in a 2 year period once. He just drove them too hard.
I'm not saying there's no truth to it, or that there isn't a general trend of foreign cars lasting longer. I just think that driver care plays a big role too.