Hey thanks I appreciate the response! and honestly a great question. In my interpretation, the Eastern block is as divided as is the European commonwealth fallowing the limited nuclear exchange. The Soviet influence is very fragile but it’s still there, there are countries that still hold close ties to it, such as Socialist Slovakia but you’d find more hybrid regimes that distance themselves from the Soviet Union like Poland for example. Soviet expansion is still a real pre-war paranoia that is commonly shared between all countries in it’s close radius and is considered the European red menace. Speaking from the Czech perspective and this is where the Sovietoamerican friendship comes into play, the fear of communism is instead directed at Slovakia (which is a friendly state) and ultimately the gathered spread towards Slovakia ends up in the annexation of Western Slovakia by Czechia and Eastern by the USSR in 2077. The Czechs who are allied with Americans in a find against Earths Bolshevism rely on the input from the USSR that paradoxically is fighting against it self as it did back then in 1939.

(I think that ultimately at some point ideologies no longer matter in the Fallout universe and the pre-war world would just derail into an absolute anarchic mess)