Yet in its current dour mood, Europe risks

问题：

Yet in its current dour mood, Europe risks almost overlooking the revolutionary step forward it has taken in creating the world’s largest and wealthiest barrier-free market—and on a continent where, for centuries, economic battles have led to some of history’s bloodiest wars. Moreover, a failure to reinforce the single market by pushing forward with European integration could lead to an unraveling of what the internal market program has achieved, some observers say.