it was back then, especially during the rise of liberalism and nationalism.
monarchs were actually quite happy with diversity. it simply meant more power to them.
liberalism contained within it a 'right' of 'self determination'....hidden in the phrase "no taxation without representation".
Now i am not a liberal myself, of course. but that aspect of liberalism agrees with my own perspective...and happens to be the only part of liberalism that was discarded in the 1960s