I haven't been keeping up with this issue as well as I should, so I may be a little out of tune here, but I have seen several trends in these, and other, comments, which bother me.

As to why the US is involved at all, while not getting involved elsewhere, this is quite simple. So far, this is the only country where armed rebellion has broken out, the "freedom fighters" actually taking the field against the military. Additionally, these rebels specifically called for help from the UN. As a part of the UN, and of NATO, it is perfectly acceptable for the US to become involved. No declaration of war is necessary, so no input from Congress.

The change of government in Egypt was accomplished mostly through (relatively) peaceful protests, with the military taking a back seat for the most part. There was no request for aid. Therefore, no reason to intervene. The same applies to other countries which are experiencing these problems. (Syria may be the next stop for the UN, though. Things do seem to be getting out of hand there, too.)

As for the complaint that the US is only looking out for its own best interests, well, DUH! Whose best interests SHOULD we be looking out for? People complain when the US interferes, then complain even louder when we don't. Maybe we aren't taking on your particular cause and you feel slighted. Tough shit. Like any other nation, the US must FIRST look out for its own interests, as perceived by the politicians. Unfortunately, this generally means what is best for the corporations which control the politicians, not necessarily for the people who elected them. But in reality, how is this different from any other nation around the world?