And thanks to your grandfather Germany is a free country now - again, this is what the Germans are thankful for. On the other hand - I am not responsible for my grandparents' generation's wrongdoings, neither are you for slavery or killing indians. So cut the nazi crap.
As opposed to the terrorists, who commit horrendous (no one is trying to not at all to legitimise this) crimes and torture, the US's administration is sworn in to spread freedom and democracy. They put themselves into a bigger league - and on this point they seem to be having trouble.
I guess I won't be able to take away the impression that I hate your country - for the record, I don't - actually, I see it as a sign of respect to exercise the rights given to us (partly because of the US). If your point is that because "we Germans" are indebted to the US, and should therefore shut up, I would argue that the spread of freedom and democracy seems not have been successful. I assume that it isn't, because it would show a poor understanding of the basic rights that keep our democracies afloat.
Oh my. What can I say to that? As Milton Bennet said, just having been present does not mean that automatically a learning experience ensues. I would have hoped from someone who has "been there" (I hope you haven't seen any abuse, because you would have had to report this), your view would be a bit more differentiated than just "be thankful Germans, and shut up".