It's happening, Apple!

Google's free and open-source Android operating system shot past its competitors last quarter to become the top-selling U.S. smartphone OS, according to research firm Canalys.

Android accounted for 34% of the 14.7 million smartphones sold in the U.S. last quarter, while RIM was 32.1% of the market and Apple was 21.7%, Canalys estimates. That's a huge victory for Google, which was zero two years ago. (Related: "Congratulations, Google: Android Is A HUGE Success So Far.")

Yes, Apple's iPhone 4 didn't launch until the very end of the quarter, and Q3 should be bigger for Apple. But the fact that Google is anywhere near Apple's market share -- let alone halfway above it -- must concern both Apple and RIM.

What does it mean for Apple? It's time to start selling the iPhone at more U.S. carriers, and not just AT&T.

Apple must sell the iPhone at Verizon Wireless, the biggest U.S. carrier, as soon as possible, and potentially at T-Mobile, too. In the U.S. smartphone market, carriers still handle most of the distribution -- Google learned this the hard way when its would-be-disruptor Nexus One store flopped. And now only about a third of iPhone buyers are switching to AT&T from other carriers. So if Apple wants to take the top position in the market, it's going to have to sell the iPhone at more carriers.

What does it mean for RIM? The new BlackBerry 6 platform, which is expected to be unveiled at an event tomorrow in New York, had better be VERY good.

RIM led the U.S. smartphone market for a long time based on its strong brand and distribution across all major carriers. But RIM has totally dropped the ball when it comes to evolving and improving its platform: It missed the boat on touch phones, its app platform and web browsers have been terrible so far, and the main reason that it's still selling so many BlackBerry devices in the U.S. are super-cheap deals and buy-one, get-one-free offers. If BlackBerry 6 isn't a huge improvement, RIM could wind up stuck at the low-margin, low-end of the smartphone market -- not where it wants to be.

Of course, RIM co-CEO Jim Balsillie has already promised that RIM's new platform and its new gadgets, coming this year, are "a quantum leap over anything that's out there." So RIM is totally safe, right? Right?

I don't agree with my colleague Henry Blodget, who writes that Android could do to Apple what Windows did the to Mac -- totally dominate the market and make Apple completely irrelevant. The smartphone market is too fragmented and too diverse for this to happen, even if mobile apps provide a kind-of platform war the way desktop apps did.

I think there will be two or three big smartphone platforms leading the pack with 25% to 40% of the market each, and the rest playing for the scraps. I think it's likely that Apple will be one of the leaders, and now it looks like Android -- not RIM or Palm or Microsoft -- will be the other big one.

But Apple is no longer the obvious no. 1, and whether it ends up as no. 1 or no. 2 in a few years is now up to Apple, and how badly they want to lead or follow.

Related: Congratulations, Google: Android Is A HUGE Success So Far