Any Americans traveling to Europe starting in 2021 will need to register for an ETIAS (European Travel Information and Authorization System) prior authorization.
The bottom line: To get the new approval, Americans need an email account, a valid passport and a credit or debit card. Once obtained, the proposed ETIAS authorization will be valid for 3 years. The EU cited a need to improve security levels and to avoid "illegal migration and terrorism" as a primary cause for the ETIAS requirement.
Go deeper: Here's what else the EU is up to.
Editor's Note: The language in this article has been corrected to say the EU requirement is not technically a visa and that it was not announced today.