Although I certainly don't blame anyone for thinking of right-wing terrorism as primarily domestic, some degree of research will demonstrate the multi-national nature of the problem.
We can start with The Base, founded by Rinaldo Nazzaro in 2018, the year after he moved to Russia and obtained Russian citizenship. Nazzaro is a longtime advocate of Harold Covington's Northwest Front concept -- an all-white state in the Pacific Northwest. Nazzaro purchased properties in Washington state for training purposes. The Base was active in Canada, the US, and Europe -- members were arrested for planning a mass shooting in Virginia at a gun rights rally in 2020, for planning to vandalize synagogues in Wisconsin and Michigan, and the Ukranian Base cell claimed responsibility for assassinating an intelligence officer in Ukraine's Security Service. Nazzaro remains in Russia, safe from prosecution.
In 2020, Robert Rundo started the Active club network, which promotes mixed martial arts as preparation for a race war. Rundo also moved to Europe to avoid US prosecution. (He has since been extradited from Romania.) These clubs have absorbed a number of former Atomwaffen Division members. Active clubs have not gone as far into terrorism as The Base, but have played a role in a number of racially-motivated riots in the British Isles and there's some evidence of terrorist-flavored plotting among specific Active club instances.
(It's worth noting that these clubs are decentralized in a similar fashion to antifa groups; Rundo is not a central authority, although he's more of a central figure than anyone who considers themselves antifa. But I want to be consistent.)
Speaking of Atomwaffen -- I don't consider them as much of a threat as they were prior to 2020. However, since we're talking about foreign coordination and support, it's worth noting that they emerged from the Iron March website, which was run by Alisher Mukhitdinov, who is believed to be an Uzbek living in Russia. Mukhitdinov claims he was recruited by Aleksandr Dugin. In any case, Atomwaffen was tightly coordinating with Sonnenkrieg Division in the UK and Feuerkrieg Division in Europe. And as it faded, some members went to Europe, seeing the Ukraine (and the Azov Brigade) as a potential training ground/sanctuary.
The accelerationist white supremacist movement is fundamentally international.