As the numerous other commentators have identified, people are bringing up politicl institutions because your key point proposing differentiation is defined by political institutions, such as the American revolution, but fails to account for continuity and evolution of cultural institutions that persist beyond those changes. Like continuity of the tossed salad blend of Americans.
But, my original comment to you is that noting continuity and shared evolution of cultural institutions between America and Europe during the industrial revolution is not American Exceptionalism, and isn't really something to have umbrage regarding when others note it.
Well the revolution was ostensibly the founding of America so that seemed the place to start the discussion of American identity. But it’s a fair point that the actual beginnings were was earlier, somewhere between 1607 and 1776.
But, my original comment to you is that noting continuity and shared evolution of cultural institutions between America and Europe during the industrial revolution is not American Exceptionalism, and isn't really something to have umbrage regarding when others note it.