IM *is* texting in North America

danah boyd points out the central feature of texting in North America: instant messaging on mobile devices has leapfrogged adoption of SMS:

Adults don't get the importance of text, particularly AIM text. And the Sidekick understands that American kids are mostly on AIM and it's a central feature, not a pain in the ass add-on. This is what texting looks like in the States. Turning AIM texting into a gameboy and voila! apophenia: why i love my sidekick

(emphasis mine)