To be fair I did figure out a way it could be plausible (in a manner): Soviet invasion during the early cold war. The Soviet Union overruns Europe, and the USA for some reason or another doesn't interfere. The commies set up a Central European Union to act as their puppet, or maybe as an SSR (all the SSRs being shown as independent on this map) while they proceed to take Germany. Spain meanwhile has at some point had a communist revolution and is on the side of the Soviets, taking the chance to annex Portugal while attentions are elsewhere. They then together with the SU plow into France and the lowlands, and France and Britain in desperation form a union to help tackle the commies, managing to convince the Irish to join in as well. The newly conquered communist Italy puppet is given some land as well, and a new Anschluss (with Switzerland being partitioned!) is arranged to united as many Germans as possible under the DDR. The area in the lowlands and eastern France is a Soviet occupation zone. Presumably the Soviets have also taken Scandinavia in the process, and for some reason created a Baltic SSR out of Latvia and Estonia. Neither France nor Britain has had time to withdraw from the middle east properly when the invasion comes, explaining the united Levant (being a Franco-British colony).
That would explain it fairly well I would think, although you'd need to explain why the USA isn't doing anything.