Formerly economic backwaters, many Central and Eastern European nations have boomed in recent years, offering a growing list of exports and eagerly buying Western goods and services in return. Now the gains are unraveling, another casualty of the world financial crisis. With the region no longer isolated, an economic collapse could reverberate in the West, as Central and Eastern European borrowers default on an enormous volume of loans that Western banks were all too eager to grant just a few years ago. Many economists warn of a treacherous feedback loop, with problems in each region compounding those in the other, and some fear that Western Europe could even be flooded by economic refugees from Ukraine or other Eastern countries, as it was during the breakup of Yugoslavia in the 1990s. “The whole world is interlinked now, so we have to care about Eastern Europe,” states Wharton finance professor Franklin Allen .…