https://en.wikipedia.org/wiki/Shield_laws_in_the_United_Stat...
"There is no federal shield law and state shield laws vary in scope."
https://www.mtsu.edu/first-amendment/article/1241/shield-law...
"There is no federal shield law"
Not even former or sitting presidents are protected.
> possessed by a person reasonably believed to have a purpose to disseminate to the public a newspaper, book, broadcast, or other similar form of public communication, in or affecting interstate or foreign commerce;
"Journalist" is merely an informal summary of what the law actually states.
If everybody is a journalist, then there's no ambiguity. But if the law says that some people are journalists and some people aren't, now there are two classes of citizen and it isn't even clear which is which.