You can guess, but you will often guess wrong. There are people that look typically X and they are from X, but there are also people that look typically X, but are from Y.

you can tell by their facial features where they are from most of the time. something that i found intersesting was when trying on motocross helmets i found that Suomi Helmets which is a European brand they tend to be made for a narrow long face and Bell helmets tend to be designed to a round head. Which makes sense Europeans tend to have a longer face then the american round head. Maybe it is a random thing but i am not the only rider to say this.