from my experience the US seems to have more stop signs than anywhere else... for whatever reason (over-zealous traffic engineers or incompetent drivers) almost every intersection in the US must be fully regulated with a traffic light, 2-way or 4-way stop sign... the yield sign is usually only seen for lanes merging and rarely at intersections and a completely unmarked intersection (except for in the country) is almost never seen.

i think most of Europe has rules for unsigned intersections (in germany the 'right-before-left') and then usually has signs marking who has right of way at most intersections (yeild sign for the smaller road) as well as far more round-a-bouts... traffic lights are also much less common in Europe.

on many smaller roads in the US, every other intersection has a stop sign ever few hundred feet or less (inner-city Portland Oregon for example)

the first few times i drove in Europe i was surprised when i came to unregulated intersections b/c you just don't see them in the US...