There are two issues here, which often become entangled. The first is European attitudes to the contemporaneous American administration, and the fact that reflects on Americans traveling abroad. Sometimes we get cheered, sometimes we suffer guilt by association, and sometimes we are asked how we could be so stupid. The second is reaction to the occasionally boorish behavior of American tourists: we are perceived as too loud, we tip too much, we are too direct, too much in a hurry, too complaining when things aren't exactly as we find them at home.
My usual approach is to distance myself from unpopular presidents, and try to be a quiet and respectful visitor. People will respond to you as an individual if you give them the chance.
And - oh by the way - we should return the favor.