As far as us being 'the good guys', I think there are some objective standards by which you can judge that.
1) Being accepted by the population of the invaded country as liberators. I think the jury is still out on that, but I'm hopeful it will be the case.
2) Working within the laws and guidelines established by the international community. In this respect, we've earned a big fat F; in fact, it seems to be our intent to destroy the entire fabric of international law.
3) Setting an example of integrity. Another big fat F. I can't think of any similar time in history where the US has bent over backwards to portray itself as shallow, shortsighted, bullying, and dishonest.
4) Sacrificing our own resources for humanitarian purposes. I think our national self-image in this regard is grossly exaggerated, if you compare our enormous weath with what we devote to humanitarian aid; but every nickle tossed in a tin cup demonstrates some charitable instinct, anyway. But a recent poll is disquieting-- it seems about 53% of Americans are in favor of appropriating Iraqi property to 'pay for' our invasion of their country. Further impoverishing this put-upon country would be absolutely unconscienable!
Finally, my faith in our status as the 'good guys' is tempered by doubts about our national morality and even sanity. I remember a conversation I had with a co-worker, a completely normal and typical person and a devout fundamentalist Christian, regarding the threat to our jobs by 'offshore' outsourcing, i.e., having our programming work done in New Delhi or Singapore. In complete seriousness, he said 'Maybe we have to drop an atomic bomb on them.'
If our comfortable lifestyle was threatened, would the American public support the conquering of other countries to acquire their resources or eliminate them as market competitors?
Sadly, I think with the Iraq invasion, we've come much closer to finding out.