After July 31st. 2025:
All dogs entering or returning to the U.S. must be accompanied by a CDC Dog Import Form receipt.
Dogs coming from dog rabies-free or low-risk countries do not require any other documents, but must still meet other requirements, such as appearing healthy, having a microchip, and being at least 6 months of age.
Dogs coming from high-risk countries will need additional documents.
CDC required form:
https://www.cdc.gov/importation/bringing-an-animal-into-the-us/index.html