Basically the title.
I have seen the EU-OS/Suse discussions for some months now. However, Ubuntu/Arch/Fedora are extremely mature projects. So competing against them will be hard.
I want to know how realistic the scenario (described by the question) is.
This has been done by Github several times. But thankfully, all major distros are not primarily hosted by Github.
However, I am unsure how powerful sanctions are on distros if the US becomes relentless.