I agree with meyer, my S3 has been rooted forever but has never been recognized by my kenwood deck. But it'll see a crapple device instantly, and i never once thought to blame my phone, it's the deck and i know it. Even a bunch of my car club buddies have top shelf big $$$ stereo decks, and those don't even see our phones, galaxies, droids, notes, etc.... But they see crapple just fine, even ipads. Crapple pays manufacturers to integrate with their products, that's why the market is flooded with them.
So to get your android phone to play on a car stereo thru usb, look at the deck specs. That's where it all comes down to. The stereo manufacturer. There are more and more stereos coming out that integrate with android, you just have to shop around. I even saw a new kenwood that has an app that'll stream your music to the deck via bluetooth! But if that's still not good enough for you, then go be an isheep!!