[ClumsyPilot]

Range of possible reasons -

Maybe because issues in poor nations are straightforward to solve: if you resolve the issue with clean water for a village, that improves lives of hundreds. Issues that plague 'The west' don't have a known solution.

Maybe because of most issues in poorest nations is lack of funs / tech, which he can provide, but cause of suffering in western world is usually political or mismanagement, which he cannot 'provide'

Maybe because for the same resources deployed the choice is between saving 100 kids from disease in Africa vs helping social mobility of 1 kids in US

Maybe you do not believe that from Alaska to Hawaii is 5,000 miles of "we", but 500 miles South from Texas it's "they". Nation-centric worldview is a relatively new idea that only existed for a couple hundred years, even today many people associate by faith, by town/province, by ethnicity or other things over nationality