American history and culture is heavily influenced by the Protestants that made up the early US. The Protestant work ethic is a commonly referenced aspect of American culture, and most Americans regardless of religion are not free of its influence.
Many cultures, in the far east as well as Europe have similar "always be doing something productive" undertones.
I agree that the moralizing zealots that set the tone for early American culture were insufferable (and being so insufferable likely helped accelerate the settlement of the east coast states) but "muh protestant work ethic" isn't really unique to the US.