This is not just for USA visitors and has been discussed at length in the past on the forum
From 2024, If you are a citizen of any of these countries
And want to visit any of these countries
Then you will need to apply for an ETIAS before travelling
Full details can be found here
New requirements to travel to Europe
ETIAS
Official EU website on ETIAS, the new travel authorisation for visa-exempt travellers to enter 30 European countries. Applications should be filled in this website from 2024.