From CNN :
The European Union is considering requiring Americans and Canadians to apply for visas, even if they only want to come for a short break.So why the tougher line? European officials say they may suspend a visa waiver program for the U.S. and Canada because they still require citizens of some EU countries to apply for a visa.
While Americans and Canadians only need a passport when visiting the EU, visitors to the U.S. from Poland, Croatia, Cyprus, Bulgaria and Romania need a visa. Romanians and Bulgarians also need visas for Canada.