As an American who has been living in France for the past 10 years, I can certainly offer a lot of advice about living abroad and about traveling. Most Americans assume that others will love them when they travel - since they are helping the economy, showing an interest in the country, and offering their support. This, however, is not always the case.
Not everyone loves America. I know this is difficult to hear since most of us are so patriotic and attached to America. It's important to understand, however, that many people in other countries enjoy their country as it is - and they don't necessarily welcome foreigners to come and loudly walk through their streets.
With this in mind, here are a few pieces of advice. Don't wear obviously American clothing, including items with American flags on them, baseball hats and GAP t-shirts. Try not to wave your map around as you walk down the street. Map out your route in the morning and try to be subtle about your confusions. Don't assume that everyone knows English, or that everyone wants to talk to you.
Remember that, while you are on vacation, the people you meet are going about their daily lives. Try to respect their space and their country. And have a great time!