Destination: France | some basic information and travel assistance

For US Citizens, very easy. And part of Schengen Area, so once in Europe you are fairly free to travel in and out of France to other countries within the Schengen Area.

All of France remains at a Level 2:
Exercise Increased Caution
Exercise increased caution in France due to terrorism and civil unrest.
US Government Travel Advisory Page for details

ETIAS required starting 2021
Starting in 2021, the European Commission will roll out a U.S. style electronic travel authorisation system for visitors from countries that are currently not part of the EU or Schengen Member. The cost of an ETIAS is €7, however, individuals under the age of 18, or over the age of 70, will not need to pay the fee. The ETIAS must be applied for online prior to arrival to the EU. Each eligible traveller, regardless of age, will require an ETIAS to visit EU member countries. The ETIAS will be mandatory for citizens of such countries as the United States, Australia, New Zealand and Canada.

for more information, visit the Official ETIAS site