Cask beer is undergoing a resurgence in Britain, with sales rising in a declining market, and the range and quality constantly improving. Yet, despite the "craft beer revolution" continuing to grow in American they still lag woefully behind Britain. If you're lucky a craft beer bar may have a single cask ale on, in all probability with a cask breather, a far poorer state than would be found in a bog standard British boozer. Over the pond dull and lifeless* keg beer predominates.
The Brewers Association is almost single handedly responsible for holding back cask beer in American brewing with its emphasis on innovation and an ever growing range of weird and wonderful beer "styles". This innovation is less than helpful. You're more likely to find a pumpkin beer than a cask beer in the states. The constant push for progressions means the tremendous tastes of traditional beer are forgotten.
Though diversity is a great thing it shouldn't take priority over quality and the best way to get awesome flavour from a beer is to serve it from a cask.
*Until re-animated with extraneous CO2.