I moved to the US in the summer of 2004 - almost five years ago. And while the UK and the US are close cultural cousins, there are still enough differences to make me chuckle.
What, for example, is with all the "STOP" signs over here? Especially since you're supposed to come to a complete STOP at them. In the UK, those are rare. In most cases, they use the UK equivalent of a "YIELD" - they call it a "Give Way" sign. And guess what; there aren't piles of car wrecks (they call them "crashes") at every corner. In fact, road safety seems (I don't know what the stats are) much worse in the US. I don't think I had ever seen a car on its roof before I came here. Now I've seen several. I think part of the problem is the fact that here you have high speed (50mph+) roads with no central median (called a central reservation" over there). As a result, it's not difficult to get wrecks at combined speeds of well over 100mph.
Another road signage difference is the way off ramps (UK "exit lanes") are marked. In the US, it's common for the inside lane to simply become the off ramp. As a result,if you do nothing you leave the highway or freeway (UK "motorway"), and you have to take an action if you want to stay on. In the UK it's usually the opposite. You have to decide to change to the off ramp. If you stay where you are, you stay on the highway.
The message conveyed by the position of the exit sign is different too. And that applies to all overhead freeway signs. In the UK, an overhead motorway sign applies to the lane below if all or part of is above the lane. And, most important, if the sign does not touch your lane at all, the lane specifically does *not* go to where the sign says. In the US it's more fuzzy. Usually the yellow "Must Exit" sign applies only if it *completely* covers the lane in question. If it only half covers, the lane probably allows you to exit, but it doesn't force you. But I know of at least one exception to that in Austin. And then for general directional overhead signs, just because your lane is not covered by a sign does not mean the sign doesn't apply to you. It can all be a bit confusing.
On road signs then, I think the UK has the edge.
UK 1, USA 0