Very often there is a difference between what a soldier fights for and what his country does.
America just happens to be a very good example and sets herself up a little bit. Nobody is insulting the memory of American soldiers who have fought in some very bloody wars for some good causes (WW1 and WW2 are examples, even if they where a tad late to the party
).
But the US government is very shady, as are ALL governments and when an administration takes the moral highground they open themselves up to criticism.
We have such a great example today. The UK and France are happily blowing Libya's milliary to hell because Gaddafi was being a naughty boy. Funny thin is the bastards in Bahrain and Syria are doing the same thing and yet we are ignoring it (Russia is throwing a blanket over Syria and Saudi is supporting barhrain, who the Uk and US have cosy trade links and arm deals with.)