You might be interested in this older thread Why do the many "political labels" - left/right/socialism/capitalism/etc - seem to mean such different things in the US and Europe? What is the history behind that?. Way down in thread I note:

What's really different in the two places is the word "liberal", which in America tends to indicate left social-cultural (progressive) values and in the rest of the world tends to indicate right (free market) economic values. In practice, this can usually be cleared up with the phrase "political liberal" for the American position (what Wikipedia called Social Liberalism) and "economic liberal" for the term as its commonly used in the rest of the world. I'll defer explaining why this is different to others, but I believe that ppart of the reason is the classical liberal platform (a gradual extension of suffrage, free and fair elections, civil rights, freedom of the press, freedom of religion, free trade, private property, etc., all enshrined in a constitution) has basically won the day. In one sense, "we're all liberals" rather than revolutionary Marxists or monarchists or radical anarchists or fascists or mercantilists or theocrats or something like that, though I'm no political philosopher and certainly some classical liberal thinkers like Hobbes might say we support bloated states and bureaucracies.

Though I think /u/watermark0n is right to point that contemporary Libertarian positions aren't necessarily identical to the "Classical Liberal" position. The rest of the world does use the American sense of the word when it talks, for example, about "liberal" and "illiberal democracies".