In an effort to thwart potential threats, the European Union is going ahead with its new European Travel Information and Authorization System (ETIAS), by which folks coming from the United States and another 60 countries (including Canada, Mexico and Australia, among others) will have to register before entering the various destinations that make up Europe's Schengen Zone. 

Currently, the Schengen Zone is comprised of 22 countries that are also part of the European Union, plus four non-EU ones and three European micro-states. Here is the list of countries that will require you to register prior to entering: Austria, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, and Switzerland. San Marino, Vatican City and Monaco, three micro-states, are also part of that list.