Earlier quoted context omitted.
Are you referring to economic Liberalism (classic or otherwise) or something else?
Not economic liberalism, more political liberalism.
Post cold-war there was maybe a few years or less of Fukuyama-esque optimism. The Arab Spring looked positive and ended with most places worse than they started.
So - not sure there was much of a window of invincibility. Unless of course you want to hark back to the Fin de siècle period. Imperialism was in full swing so that's controversial.