Because benefits to people far away that you never have and never will directly observe seem abstract compared to the needy at home, which higher economic classes already ignore plenty.
We are individuals, not a blob of goo. Self preservation and acquisition of personal wealth are some of the fundamental drivers that have ultimately benefited our species.
Considering us as individuals is to an extent an ideological way to view the world. On the contrary, what you said can be said about cooperation and sharing too. See Kropotkin's Mutual Aid.
Huh, I thought it was well-known that many borders were drawn arbitrarily.
India / Pakistan is one example. Lots of middle Africa. Basically anywhere where colonialism played a major role and there wasn't an ocean or giant mountain range to make it more obvious exactly where to 'draw the line' (usually fairly literally).