I do think we're involved in some minor way in most conflicts, even if by not doing anything at all. When you get this big and powerful and economically interconnected, it's hard to completely ignore something - if you trading with somebody is normal and economically necessary, then not trading with them is an intervention.
The reasons behind any particular policy are of course complex. Some may be for good and noble reasons, others for not so good reasons. A few turn out well, many go badly or not at all as intended.
Many people in foreign countries even try to get us to intervene. Often they want us to fund them or to suppress their enemies. Some want us to suppress violence in other countries, just because they think we can - see Darfur. Their motives aren't any cleaner or dirtier than ours are, just saying we aren't uniquely or cartoonishly evil.
I think the important part to remember is that our real ability to change things abroad is very limited indeed and fraught with risk. We can nudge things a bit, sure. If a country is on the verge of civil war, we can maybe nudge them towards it or away from it, but we can't create the war from scratch, or control what the sides are. If they really want to fight, they will, and we can't stop them. If they really have no desire to fight, we can't make them. If we try to nudge, we may just cause the opposite thing to happen instead. It's a mess, and it's likely to continue to be a mess no matter what we do or don't do. There's always the hope that we can encourage things to be a little bit less messy, but that may not be in the cards.