I've often heard that in countries outside of the US, libertarianism itself has different meanings than what Americans first think of
That's something of a countermyth. While Chomsky does indeed describe himself as a libertarian socialist, it's telling that he has to qualify it (because leaving out the 'socialist' part would not leave people thinking, well, he might be a conservative). Most of the big names in libertarian philosophy like Hayek or Mises have been conservative libertarians who, even if they didn't necessarily describe themselves that way, in practice found they had far more in common with the traditional right than the traditional left.
This isn't to say that left libertarians don't exist or shouldn't call themselves libertarians, but they don't really have every much in common with other libertarians.
In practice, the "pot smoking Republican" is a pretty good description of a lot of the people who will call themselves libertarians. It's a little broad, but it does accurately capture that their departures from conservative orthodoxy are confined to lifestyle issues and generally in areas where conservative orthodoxy doesn't represent the consensus, so defecting is low cost. Conversely, a lot of these guys will support traditional conservative policies in ways that are deeply anti-libertarian - for example, they are often in favour of enhanced border security or reduced rights for non-citizens, both of which are intensely opposed to the fundamental principles of what libertarianism is supposed to be about, e.g. a small state. They will sometimes complain about Wall Street or corporate welfare, but are usually short on specifics about how to do something about it, so it's hard to take it seriously. (Not to mention that in some hypothetical libertarian governance system, Wall Street would flourish)
American libertarians have some particular quirks that other libertarians don't have. Because reverence for the US constitution is a requirement for everybody engaging with US politics, libertarians are required to claim that the USA is the most libertarian country in the world, and that a true American patriot would be a libertarian. (Social democrats, of course, are required to make the same claim) Libertarians saying this are not quite as jarring as social democrats - while it would be wrong to say that the Founding Fathers were libertarians, their 18th century Enlightenment-derived conception of a decentralised state isn't the worst fit for libertarianism. But that's more of an indictment of the US constitution than it is an endorsement of libertarianism.