In some cases, the president of the country has attempted to meddle and directly intervene in such matters, in ways that are sometimes patently unlawful.
Wha? Unlawful? LOL When did this happen?
If you're comparing this to the NFL stuff you are comparing apples and doorknobs. The NFL players were doing their stuff on the field, not on social media on their own time, HUGE difference.
I don't see the distinction you're raising about "on the job" vs. "social media" as being significant. A lot of the NFL protesters did so on the field with the blessing of their team's owners.
I was referring to 18 U.S. Code § 227 which criminalizes actions of elected federal officials who seek to influence the hiring and firing decisions of private entities. And I'm aware that many pundits, including the liberal WaPo, have scoffed at this idea because the intent of this law requires the interference to be solely based on "partisan political affiliation" which is Congress's polite term for "party membership."
However, since it's Saturday night I'll put on my Internet Lawyer uniform and you can do the same if you like, but I'm only gonna make one run at this and not come back to it because I don't want to derail the thread into US politics.
The term "partisan political affiliation" does enjoy a lot of customary use, but I'm unaware it's ever been given a legal definition by statute and only a cloudy one (at best) in case law, simply because parties are extra-constitutional creatures and nobody wants to talk about them in court if they can help it.
Consequently, since the president (1) called Kaemp a son of a bitch in public speeches, (2) tweeted that he and others should be fired, and (3) specifically took personal credit for the fact that Kaemp ended up jobless and unemployable, I'll bet a bunch of money there are attorneys out there who'd be quite happy to sue in the Ninth District where Kaemp and his former team happen to live. And they might get somewhere with it, the Ninth being a huge blister on Trump's ass every chance it gets.
There is additionally the issue that the president swore a constitutional oath to "faithfully" exercise the duties of his office, and while this is more a matter for Congressional oversight than it is for lawsuits, I'm also not aware that the exact legal or constitutional definition of "faithfully" has been authoritatively sorted out.
That's my shot, pal. Knock your socks off.