I think I will try and find a system today. So far five Wal-Marts, five Gamestops, a Target and a BestBuy... all sold out of all units. Games are plentiful though.
I'm assuming you are talking about the deluxe? Nintendo clearly didn't understand demand properly and whoever in sales was responsible for making so many white units will probably lose his job.
When things start to sell out in stores they are sold out online even sooner. It always happens that way, scarce products are sold out online then you need to look in b&m's for it. That's what's happened with the deluxe. The fact that the basic unit can be purchased online shows that there is plenty of them out there.
It's also possible no one wants the basic unit bundles which is what can be purchased online from Walmart but if things were really bad with supply then those bundles would be sold out too.