No, they are not. The US legally recognized Taiwan (fka Formosa) as Chinese territory in 1943 and 1945 and legally recognized the PRC as the sole legal government of China in 1979, following a similar recognition by the UN in 1971.
https://www.congress.gov/crs-product/IF12503
There are only 11 countries in the world that recognize Taiwan as a sovereign entity and the largest are Guatemala, Haiti, and Paraguay.
https://en.wikipedia.org/wiki/International_recognition_of_T...
It is de facto a country, not de jure, for obvious reasons. You can pretend otherwise, but what's the point in engaging in a discussion where you get to invent your own reality?