First off, the Japanese put their cars together well. Far more care is put into production quality than American cars.
Secondly, we all know how competitive the Japanese auto industry is. People forget that Japan has to import every resource required to produce cars - unlike the States. This is a massive expense and depsite this Japan consistently produces vehicles that are comparable in price to U.S. vehicles...and invariably better in quality.
Finally, in all of my travels, to see an American car outside of the U.S. (excepting Canada and Mexico) was rare to the point of being unique. I saw Japanese vehicles EVERYWHERE - even in Afghanistan it wasn't Land Rovers or (chuckle) Hummer's those muja's were bouncing around in. The were Toyota Land Cruisers - most over ten years old, beat to hell and STILL running great. Japan drives the world.