Clean cycling cultures: anywhere where there isn't much money. The road scene in US/Oz/UK/S America is always going to be cleaner, at least in terms of efficacy if not morality, because there's no money. No-one's going to get on a proper programme unless they're any good, in which case they're going to go to mainland Europe anyway. I'm sure people are doping on speed and steroids and whatnot in Premier Calendars, but there's no-one on blood transfusions or CERA because they can't afford it, and if they could afford it they'd be doing it in Italy or Belgium where they can ride proper races.
Dirty cycling cultures: anywhere where there's the possibility to make money and/or be famous. Belgium, Netherlands, Spain, Italy, Luxembourg, parts of Germany. Not riders from those places, but riders that end up in those places.