As someone based outside of the US, I rarely see people with stickers on their laptop. The very vast majority of cars also do not have bumper stickers here (and those that do might have one at most).
I see them at technical conferences in many different parts of the world, with people from many different parts of the world. It's not a US thing.
And many of the sticker pictures on this site appear to be from European countries, including at least Finland and Germany.
We do have a lot of stickers on cars too but it's more common to see them on windows of the car not the car body, and I think in general they're socially quite different to what you'd see in America. More like brand stickers and hobby stuff, or jokes, not so much politics or religion.