I read on :
https://www.iatatravelcentre.com/world.php (-> Costa Rica):
Costa Rica. > Published 15.10.2020.
- Passengers are not allowed to enter.
This does not apply to:
residents of the following states of the United States: Arizona, California, Colorado, Connecticut, Florida, Georgia, Maine, Maryland, Massachusetts, Michigan, New Hampshire, New Jersey, New Mexico, New York, Ohio, Oregon, Pennsylvania, Rhode Island, Texas, Vermont, Virginia, Washington, Washington D.C. and Wyoming;
How does one prove one's residency to a given US state when flying to Costa Rica?