I actually specifically mentioned airlines operating in the U.S., which includes international flights operated by foreign airlines. But yes, you get to the heart of the matter. The U.S. in general expends more time and effort on safety: higher-spec airplanes, more crew hours and training, better maintenance, etc.

It doesn’t feel relevant to most people on this site to include airlines operating on a shoestring budget in Southeast Asia or Africa in the statistics. It also doesn’t feel fair to manufacturers to penalize them for operators that barely maintain their planes, overfly inexperienced pilots, and that lack basic safety regulation.