The last Tamagotchi to be released in the US was the Tama-Go, which was released in 2010: http://tamagotchi.wi...amaTown_Tama-Go
Stores near me, like Target and Toys 'R' Us, carried Tama-Gos and accessories for them for about a year and a half, but they then disappeared from the shelves. To the best of my knowledge, most stores no longer carry Tamas or anything related to them. The demand them just wasn't high enough.
You can still easily find all US Tama versions online, both new and used, though. I've been buying most of my Tamas on eBay, Amazon and other online shops for years. There's a nice selection out there; you just have to be patient when it comes to finding good deals and fair prices.
Oh, and new Tama versions are still being released in Asia because of their ongoing popularity there, particuarly in Japan. The most recent versions have been in color (like the Tamagotchi ID, Tamagotchi ID L, Tamagotchi P, etc.). All but one of the releases have been only offered in the Japanese language. Just a small run of Tama ID Ls were made in English; however, they're more difficult to find and tend to be on the more expensive side.
Edited by Happily Candied, 05 September 2013 - 10:15 AM.