the big picture
Are you looking at the big picture, with U.S. foreign policy? I'm not so sure. It seems that you have only pointed out some negative results of American decisions, but, I don't know...
The U.S. seems to have to be responsible for a lot of countries, a lot of the times. I hate to say that, but it seems true. It seems that most of the time, the U.S. has tried to stay out of other countries' situations for as long as they can (except for, say, Iraq, and maybe Afghanistan too) until the country absolutely cannot avoid the situation. There is a lot of "politics" involved in the politics of this, too. Such as, sometimes a country has a not-so-great leader but the U.S. can't do much about it, because maybe they need that country to be an ally, (esp. if the U.S. is at war with a nearby country) sometimes, the U.S. decides to get involved in a country (in part) to protect its own interests in natural resources that it does not have. Sometimes the U.S. cannot piss off one country because it does not want to lose a nearby country ally or doesn't want to piss off a nearby country. Then, sometimes, America, doesn't get involved in a country just when it should till later, because the country does not have important trade ties with America, or is not economically in the top priority to America.. I don't know...you touched on some of these ideas earlier.
I don't know what you are asking. Since the Cold War is over, shouldn't the U.S. act differently, and not be so "Pre-emptive?" Yes, the Cold War is over, and so the U.S. should not act just as it did with the politics of the Cold War. The problem is, the problems, politics and country issues in this world are ever changing, and perhaps the U.S. has had some success with the "better safe than sorry" method before. It is also trying to keep up with new issues arising in different countries, and seeing what it needs to stop or not, and how it would affect the U.S. or other countries.
And, however, many good results have occurred as a result of American foreign policy, though.
And, America's involvement in Bosnia and Somalia was not perfect, either. Sometimes, bad things do occur, but in the end, there may become some good, results.
America, is not perfect, but then, who said it was. Anyway, those are my thoughts, O.K.