Pretty sure they're all over the place in Japan as well, with sales averaging in the 50k level for the past few weeks. With Mario Kart and Wii Fit already out, there isn't any current catalyst for the Japanese to rush out and buy one.
The soft release schedule in the U.S. seems spaced better for continued sustained sales in terms of million sellers. Nintendo actually could have put a bigger gap between Kart and Fit.
But as it stands, the U.S. is the only market that has remained consistently pinched for inventory since debut.
Every time I saw a couple on a store shelf last year, I found myself thinking "oh, good; Nintendo can finally keep them stocked," only to find out that was a FLUKE, and that I had probably just stumbled onto inventory that had just been shelved.
Even if you can find them on shelves, it's still a fair assumption to say that in major urban markets, there is no overlap between shipments on shelves and the next scheduled shipment to be received.