Free speech is for American citizens!
Where does it say that? Where does government get any power to limit free speech for non-citizens?
THE U.S. Congress doesn't make laws anywhere but here in the U.S.
Amendment I
Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the government for a redress of grievances.
The US government has no power not given to it in the Constitution. Where is there an exception for non-citizens? Or even for protests at US Embassies? Where is there an authority that would allow the US to try a person without a jury in a foreign land? Or to hang an MS-13 member without a trial or a lawyer?
Without the Constitution, those in government are nothing other than just people. How do those people have authority of US government to deal with anyone, in any fashion, on any matter, anywhere in the world, if not through the Constitution?