What Europe has sadly become. China and the U.S. are now duking it out for controller status as First World power leaders. China is keeping the smart money in Vegas as being top dawg; they don't regulate (much) when it comes to international trade (China first, second, and third) and they have a vastly different view of individual civil rights than we do.
But there was a time (and that's not a line from Les Mis) when Europe was The Bomb. So how'd they decline so fast? From Top Dawg to meh in a century? Eh, wars were a lot of it. The continent ran out of food to feed a fast-growing and fast-eating population. Borders became conflicted. Cultural differences became a big deal in otherwise homogenous societies. Immigration (colonization) ended up being extremely expensive, sucking resources from the endemic population into them darned fawreigner interlopers. And then the countries, rather than make hard choices and opt for smart or efficient business decisions for the long run, dialed back lots and lots of playing-offense like they had for a millennium previous. They let unions run the countries; they pay low-end workers $27 an hour. And they slowly became less relevant on the world stage.
If trends continue, Europe will be largely bankrupt and just a tourist destination for wealthy Americans, Chinese nationals, Russians, and Arabs. They'd better keep their castles shiny.