The US allows antigen tests, which are cheap (or free) in many places that aren't the US (think $20 USD) and much less unpleasant than some PCR tests. They are often airport-based as well. Further, the CDC has authorized at-home proctored telehealth tests that cost $25 each and can be done instantly, without sending to a lab.
https://www.afar.com/magazine/cdc-ap...ational-travel
I agree with those who have noted that it won't kill you to spend a couple days in a new place on a run.