The racist notion of the "great replacement" originated in Europe and had many exponents of various stripes. Contrary to what is sometimes alleged, however, the phrase itself was not coined by Maurice Barres in early twentieth-century France, though he certainly believed in the ideas behind it.
The phrase, and the most extensive elaboration of the theory, originated with the French Nazi Rene Binet (1913-1957), who served during WW II in The Waffen Grenadier Brigade of the SS Charlemagne, which consisted of French collaborators. You don't get more fascist than that- the Charlemagne Brigade were the last troops to defend Hitler's bunker before his suicide, and staged a failed, desperate fight against the Soviet army's advance into Berlin.
Binet fulminated after the war against "the invasion of Europe by Negroes and Mongols," by which he meant Americans and Soviets. He saw Americans as an impure mestizo "race" (he was a biological racist). He also launched diatribes against unbridled capitalism and the ways in which Jews were using it to abet the replacement of civilized white Europeans.
So this supposedly far right American nationalist idea actually originated in hatred for Americans and a denigration of their supposed "whiteness" by the European Right, which did not see Russians as "white" either.
It is worth noting that unlike cowardly boot-lickers like Benet, the true patriots were the multi-cultural French. The French Army and then De Gaulle's Free French Army included thousands of riflemen (Tirailleurs) from Senegal. HIstory.net explains: "During World War II the French recruited 179,000 Tirailleurs; some 40,000 were deployed to Western Europe. Many were sent to bolster the French Maginot Line along its border with Germany and Belgium during the German invasion in 1940--where many were killed or taken prisoner. After the fall of France, others served in the Free French army in Tunisia, Corsica, and Italy, and in the south of France during the liberation."
I had two uncles who served in WW II, one at the Battle of the Bulge. In my family, we are not in any doubt that it was the Allies who were the good guys. And, yes, the Allies were multi-racial. They included the Tuskegee Airmen, who bombed Nazi targets, The Allies were the diverse American rainbow, and it was their diversity that gave them the strength to prevail.
People like Tucker Carlson are pitifully ignorant of history and so are wielding an anti-American, highly unpatriotic notion for the sake of their television ratings. Ironically, Tucker's intellectual forebear, Binet, would have considered him a mongrel "Negro." As defenders of illiberalism and implicitly of hatred of Jews, these useful idiots of the far right are symbolically still deployed around Hitler's bunker, defending it from the approaching Allies.