This explains the connection to classical liberalism and the confusion of these terms pretty well: https://en.wikipedia.org/wiki/Libertarianism_in_the_United_S...

You see that historically libertarianism follows directly from classical liberalism. They just changed the name.

Classical liberalism is a retrospective name for one thread of liberalism. It does not—and this is important—encompass all liberals before some date, but one branch, influenced by a set of thinkers and writers who are also counted among the influences of other branches. It has its own wikipedia page:

https://en.wikipedia.org/wiki/Classical_liberalism

and the broader thread, in context, is traced here:

https://en.wikipedia.org/wiki/Liberalism

One point that may make the distinction clear is that in this sentence, from the article you linked: "During the mid-20th century, many with Old Right or classical liberal beliefs began to describe themselves as libertarians." The "Old Right" were opponents of Roosevelt, who himself sits at the base of the branch of what the "Liberalism" entry calls "Modern Liberalism"—but both are under the tent of liberalism, as were others then and earlier whose views did not line up with libertarianism.

Liberalism was not renamed libertarianism, even just in the US, and that's certainly not what's meant by liberalism internationally.

It's not the same, but it's probably the closest thing, because European liberals are advocates of less taxes, less government regulation and intervention, less welfare state, and in general oppose any kind of socialism and Keynesian economic policies. It's quite opposite of what 'liberals' in the US advocate for, when it comes to government role and economic policies.

'Liberalism' as used when refering to Democratic Party policies in the US, is generally refered as social democracy or social liberalism in Europe.

Here's another source from Wikipedia: https://en.wikipedia.org/wiki/Modern_liberalism_in_the_Unite...