I've had people online say that the older style of frame locks would get road grit in them from the wheel and get sticky to the point that they wouldn't open or close anymore. I've never had one so I don't know about that first-hand, or if the newer ones are any better in that regard.
Why you don't see them in the US: I think it's at least two different reasons.
One is that the bikes don't come with the fittings for them.
The other is that if the locks are built decent, they probably cost quite a bit of money and so bike companies are loathe to include them as standard equipment.