Whilst it is true that "European contracts" are not used often, I have seen reports that "at will" is not even a majority of the US workforce these days.
And I don't know of any American company that has worker representation on the board of directors. There might be a few exceptions, but they would be in the extreme minority.
We simply accept the fact that the boss can (and will) fire you at any time, and the boss accepts that you can (and will) quit at any time.
