I wear running shoes while traveling in Europe. No "real" shoes even come close to fitting my feet, and if I'm going to be walking miles a day, I need to wear shoes that won't have me in agony after an hour. I wear non-designer jeans, and put my hands in the pockets, too. People can spot the American from a mile away.

I totally get what you're saying though, Emily. Being a tourist is one thing; living there and expressing an unspoken disdain for the way the locals live and raise their children is another. I'm reminded of the scene at the beginning of "Babel" where Brad Pitt's character's wife won't drink non-bottled water, and slathers her hands with alcohol gel any time she accidentally touches anything. I don't think the question is as simplistic as some here have expressed. People in the US are as a group wildly averse to a small set of risks pushed by the media (germs! ), that in many ways alienates us even further from the realities of life, both here and in the rest of the world.

Using your helmet as a "teaching opportunity" to turn the locals into little North Americans is an order of magnitude more culturally insensitive than just wearing your own. Few things IMVHO are more distasteful than an uninvited missionary (viz. the recurring cracks about Jehovah's Witnesses in "Dear So and So" and other threads).

I say think about it and do what makes you most comfortable, but if you choose to wear your helmet sometimes, you might get into risk assessment for each ride. Will you be on pavement or softer ground? Will you be doing downhill mountain biking, or lower speed riding without a lot of obstacles? Will you be riding a road bike, or a heavy upright bike that's less likely to throw you on your head? I agree with choosing a helmet that's more hat-like and less sporty in appearance ... even if it might be less ventilated in the hot weather.