Regarding the idea that the US - or the UK for that matter - should only take military action if there is a direct threat or action against said countries doesn't chime with Article 5 of the North Atlantic Treaty:
The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all and consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defence recognised by Article 51 of the Charter of the United Nations, will assist the Party or Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area.
Any such armed attack and all measures taken as a result thereof shall immediately be reported to the Security Council. Such measures shall be terminated when the Security Council has taken the measures necessary to restore and maintain international peace and security.
Again, not arguing for or against action in Syria (and not I'm suggesting that you're all a bunch of pacifist, bleeding-heart, gutless, appeasement monkies), I'm interested in how folks here would consider the situation in Europe under the Nazi boot. Should other nations stand back and tut quietly whilst millions were being gassed, shot, starved, experimented upon, etc? I'm not talking about the fact that we were already at war, I'm considering the moral arguments.