US vs. Europe Work Culture: Myth-Busting

Since lots of folks here have worked in both the US and Europe, I figure this is the best place to ask: What's the real deal when it comes to work culture differences between the US and Europe? I often hear these exaggerated stories about Americans working weekends, getting fired out of the blue, and never taking vacations. While I know these tales are a bit much, I'm curious to get the real scoop. Do Americans really put in more hours than Europeans? Can they really get fired without any warning?