I think the reason you see big beers in America is because of the craft beer revolution that is currently taking place. The mass-produced Light American Lagers that dominate the market are, well, light! Light in flavor and relatively light in alcohol.
The big beer boom here is a pushback against everything that BMC stands for. It's a way for the craft brewers to ply their craft and offer something different than what's on the store shelf.
Then of course you got craft brewer and craft brewer trying to out-do each other on size, style, etc. They want to brew a BIG beer, and Oak it, and add Bourbon flavors, etc. because they want to offer a limit edition special beer. Some of those caught on and are now always available, but generally they are considered special.
I find it interesting that although IPAs are still popular, there are other beers that are coming into their own here, like sessions ales and sour beers. I enjoy a big beer as much as most, but I don't grab one very often. They are a treat to be savored or shared. I'm actually getting more into the lighter beers, and I'm finding that I'm not a fan of the darker light beers as I expected. I tend to enjoy the lighter styles like blondes, wits, etc. And of course, Pale Ales, and IPAs, etc.
I'm also a fan of beers like Hopslam, with so much hop goodness. I have to be careful because 1 of those and I am definitely feeling it. They are after dinner watching tv or trying to play WoW "on a good buzz, making my friends mad with my Jenkins moves, keeping it interesting". I gotta laugh because my kegerator door has a REALLY loud squeak when I open it, so they know when I'm grabbing another bottle. "Oh, here we go!" he he. Of course, the two taps on the front are silent, but I rarely keg anything high test.