Often it seems like people get offended when the North American region is speicifically targeted by companies, users on this board, etc. as a reason for success. Recently, Microsoft lowered the price of the Xbox One in the U.S. to gain significant marketshare in the territory and it looks like they succeeded according to the latest NPD results. Of course people jump to the argument that US does not equal World as a way to downplay Microsoft's success.
The fact of the matter is that the United States, and NA in general, is the most important territory to have. The Xbox One, and to a slightly lesser extent the PS4, is built around services the consoles offer- netflix, xbox live, PS+, nfl network, etc. They really are media service boxes up to this point. And of course the big 3 all want to sell as much software as they can on their console. The United States has the largest market for the services these consoles have to offer. Americans love to spend money on games and these services. Internet is readily available so they are able to subscribe to services like Xbox live and PS+. Consoles by themselves don't actually make money. I doubt Sony is making much on the PS4 and Microsoft is losing money at this point on the console itself. But Microsoft knows it's important to have the market that will end up spending the most money on games and its online service. That's why they don't care if they end up selling less worldwide.
If the right market is captured, having 10 million consoles sold can be worth more than having 15 million consoles sold. Those 10 million users may end up spending more money on the said console than those 15 million users. We saw this with the Wii. It sold a massive amount but in the end market it captured did not end up spending money on it. Many services that these consoles offer are not even available outside of the United States. There is nothing wrong with focusing on a single region and making sure it absolutely succeeds in that region, especially when that region is the most spending-happy.