Luckily US is not the whole world
You have any evidence that the rest of the world is so much different? Or was your post just your personal hopes/wishes based entirely on your dislike of Xbox/playstation?
Well, there is actual evidence that many countries prefer gaming on PC to gaming on console. Many european countries (especially in eastern europe) or Korea for example. China is complicated, as always. That doesn't mean the Switch will do particularly well in these countries too, still there is the step from PC to console gaming. I did this step some time ago with Wii, but here in germany is a split between console and PC gamers, both sides are strong. If I talk with my friends about games, they often haven't heard about some stuff I talk about and one especially can be excited, until he hears it is only on console. So in countries like here in germany the statistics will be different to the US, as not as much game on console in the first place, the Switch owners will not have at 70% owned PS4 (and really not Xbox). But they might not be the strongest markets for Switch too. Looking at the numbers, US and Japan are the strongest markets for Switch, and they are heavily into console gaming over PC gaming. So it is pretty likely, that in these countries Switch owners already owned one of the two other consoles.