We lived in the US (for a while), but before the kids came along, so can't comment on the differences really.
There's definitely is a sub-set who don't seem to know how to entertain themselves - and I'd bet a lot is to do with parenting. Of the 1,000 of kids in an area, you are seeing maybe a few tens in the park? The vast majority though are off doing all sorts of (legal!) activities.
What I would say though, as a Dad of a 13yr old girl and 11yr old boy, is gently supporting/encouraging them to do after-school activities / sport clubs / scouts etc helps a lot - they make friends with other kids who aren't into the "lets just hang around the park" idea. There are so many opportunities. I particularly like scouts, they are given some independence away from mum and dad, but in a structured environment (and in uniform so no suspect clothing style!)
Not sure about my 13yr old's dress sense - but I'm probably just being "fuddy-duddy dad"
Looking back on my (UK) childhood, I think kids today do seem at greater likelihood of being exposed to excessive drink and drugs than I ever was - my first classroom conversation about drug use was on my Maryland state driving course at age of 28....
It's probably generational as much as location! Or is it just it gets magnified by the press, I don't know.
