I would also disagree with systematic change being a requirement for US assistance/involvement. Each country, and each situation, is different. Marc's correct in that such an approach does make us look like the Soviet Union with its commitment to support all "wars of national liberation."

Our fixation on systematic change, I think, reflects our own conviction that our system is the "best" and that to be worthy of our support other countries should adapt it as well. Some countries do quite well with blended monarchies, while others wouldn't know what to do with one. And our track record in many places with supporting democracies (or what we called democracies...look at Latin America) isn't all that great. Democracies can easily be spun into dictatorships by "fathers of the people" or "fathers of the country" if the proper social networks aren't in place.

Stability operations are a slightly different ball of wax in that the visible level of commitment on the part of the US is lower, so more options are available. I tend to feel that as the level of commitment rises, rhetoric (from the press, politicians, and others) actually limits the options we have available as the situation molds itself into a "victory or death" type framework.