That has essentially never been a risk for a non-appointed government employee in the United States of America, at least for the past century or so. We Don't Politicize the Bureaucracy. And that was at least in part the secret sauce to our generational success, that we could immunize the workings of the government from the pique and emotion of its leadership.
Or we didn't. Now we do. Kinda sucks.
Since ~1885 and the Pendleton Civil Service Reform Act: https://en.m.wikipedia.org/wiki/Pendleton_Civil_Service_Refo...
Submitted some historical breadcrumbs here: https://news.ycombinator.com/item?id=43686221
Well this was advice my father (an academic and lifelong straight ticket Democrat) gave me decades ago. So it was nothing specific to the current administration.
The difference is that the people affected by whim were, by design, only supposed to be the political appointees, not the civil service rank and file. Those jobs existed for as long as Congress decided that they produced useful results for the American people. Positions could be eliminated by virtue of Congress deciding that a shift in policy was needed, eg fewer Kremlinologists after 1989, but that is not a whim, that is a result of debate.
The current administration is making all positions political, and in doing so, performing an end run around the legislative branch.