I think that no matter where you are you need to be aware of one's surroundings. It doesn't matter where you are from - a target is a target. I think it is nonsense to typify someone's attire as making them more susceptible to crime.
I guess I am a little confused by the Jeans/Shorts T- shirt and sneakers comments. In my experience I never noticed these articles of clothing being endemic to Americans - not even my university T-shirts. To me - easy target means the person who is so busy looking up and around that they don't pay attention to their own person - where they are or how they behave.

Many people who have been pickpocketed readily admit that it was a mistake on their part. Separating themselves from luggage in a train station, hanging a purse over the back of a chair in a restaurant, allowing themselves to be distracted or show confusion, carrying valuables in an outer pocket of a backpack on the subway, etc. etc.

A friend of mine has been targeted 3 times, they succeeded the first time, but not after that. She is very well put together, nice clothes, nice shoes and she is small. The first time she was not aware of her surroundings, the other two times she was aware and was able to
stop them.