The United States "refused" COVID-19 diagnostic tests offered by the World Health Organization.

https://www.snopes.com/fact-check/us-coronavirus-test/

What's True

The U.S. did not use COVID-19 diagnostic tests produced by the World Health Organization (WHO) in favor of producing its own.

What's False

The U.S. did not turn down an offer to use those tests (as no such offer was extended), nor was it unusual for the United States to design and produce its own diagnostic tests in lieu of those made elsewhere.