Both resident and visiting Americans seem to find "anti-Americanism" in the pure fact that many Germans challenge the superiority of the American political system - and its decisions. I disagree.
Comparing the experience reported by Polish friends in Berlin, I would be prepared to agree that some or many Germans have anti-Polish sentiments: Some Germans seem to consider Poles as undesirable work mates, neighbors and customers. Similarly, it's obvious that there exists anti-feelings towards Turks and people from that corner of the world. I can not detect anything similar with regard to Americans or English speakers. Instead I see that Americans get more invitations to social gatherings than foreigners of other nationalities.

Yes, German students of all kinds are better versed in political issues than many of their American counterparts, and do in general take debates on political issues more seriously. I don't really understand why, except maybe for the Germans' historical experience of undemocratic societies up to 1918 and then again 1933-1949/1990.
Yes, Germans of all kinds are critical of how America acts in the world - and as well of certain domestic policies. But criticism of policies is better not to be mistaken for anti-Americanism.Maybe what we see is a certain disappointment with America. More than any other nation, it was America that Germans looked up to when West Germany in the second half of the 20th century was rebuild as a democratic society.
I agree with Scott that some, maybe many, Germans easily express disdain in conversations with Americans, but I do interpret these situations differently. For instance: Germans I know are in general sensitive, and disdainful, for expressions of Nationalism, Militarism and Supremacism, and may sense such messages in attitudes and utterings that very few Americans would understand that way.