> Those outside of the US who subscribe to this ideal seem heavily influenced by US culture in my experience. I'm not aware of non-US sources of the idea.
Freedom of speech isn't a "wholly US topic". It's understood and accepted in most democratic countries.
> The right to freedom of expression has been recognised as a human right in the Universal Declaration of Human Rights and international human rights law by the United Nations. Many countries have constitutional law that protects free speech.
> The Declaration of the Rights of Man and of the Citizen, adopted during the French Revolution in 1789, specifically affirmed freedom of speech as an inalienable right.[7] Adopted in 1791, freedom of speech is a feature of the First Amendment to the United States Constitution
The idea predates the existence of the US.
https://en.wikipedia.org/wiki/Freedom_of_speech