I've lived in Heidelberg for a while (with Germans) and I don't think the Americans there were really well seen. The MP cars in the streets (or the US imported cars in general), flying italian bottled water to US then back to Germany to avoid paying taxes, the fact that many American people born on German territory (children of military families) don't even bother to learn german, the gated communities etc. Plus the fact that the Iraq and Afganistan operation where headquartered there, the resentment seemed quite high.

(I just googled it and I see it's deactivated on april 1st 2013 actually)