In the past five years, I have been in the cockpit of aircraft while landing at IAH, ORD and JFK. The view of the Chicago skyline when flying in from the east is one of the most elegant sights (IMO). New York is lovely too, but obviously not the same without the Twin Towers. The view of Kingwood and Humble, TX, not so great.
My children have been allowed to visit the cockpit while over US airspace. If the captain of the ship knows their visitors and trusts them, I don't think it's a problem. Besides, who the hell is the US to mandate who sits in the cockpit of a foreign registered aircraft anyway?