If you're selling games online, US consumers will very likely represent the vast majority of your customer base, so concentrating on the stats in the US is a good idea.
Well it may just be the game I'm selling ( perhaps I'll be able to judge better when the next two go on sale, since they're both very American games ) but at the moment, US consumers are not a particularly large section of my customers. I mean, they're significant, and the largest single section, but far from the majority.