Why does the US have to get involved.
Because we’re not a podunk 3rd class nation.
Because the US has global economic and political interests (to the extent they can be distinguished).
Because non-involvement is not free, and tends to rebound upon one in unexpected ways (e.g. the Rwanda non-intervention had political effects quite unexpected).
But for those of you in the heartland, because our capital comes from overseas because you all save too little and spend too much. Investment (as reflected in the current account/capital account imbalances) is funded with foreign savings.
Thus, sitting with one’s thumbs up ones butt, gazing at one’s navel will eventually have bad effects, not obvious at first but there.
As for the P’s and terror, well the world is a complicated place and as Brezhinski recently noted, neo-Leninist those who are not for us are agaisnt us thinking gets one in trouble.
Not all conflicts are reducable to good guys and bad guys if one wishes to pursue long-term national interest.