Toyota has had to offer five year warranty to catch up with Kia seven years. Mitsubishi also tune their cars to Irish roads.
I am not sure about the car industry, but in the electronics TV etc, the quality was grade by letters ("A" "B" "C" and so on) there is no such thing as good and bad. So the best quality would go to the largest market.
My Toyota has had a HP pipe failure on the AC system after 45,000 mile I can see it is bad manufacture, but it cost me €400 to fix it, if it was a 5 year warranty it would be Toyota's problem.