@paultesoro,
I wouldn't include the UK or Europe in your reckoning.
Over here, diet drinks have never been regarded as 'something for women'.
Personally, I think that we prefer diet drinks over this side of the pond for taste reasons as well as health.
With a pile of sugar going into each can of ordinary Coke, most 'diet' drinkers over here find the ordinary sugary drinks far too cloying.