USSR swallows up Eastern Europe after WW2

[big bad fab]

What made them "swallow" the ones they did swallow though?  Were the swallowed ones already more "Russian" at the time?  What is the big difference between say, the Ukraine and Poland?  Latvia and Romania?  Georgia and Hungary?

The answer is: Russian Empire.

Apart from Poland, all the other territories were Russian not long before !
And even in the case of Poland, Stalin pushed it far away towards the West and grasped back a big part of Czarist territories there.

And Xahar is right. Putting inside the USSR East and Central European countries would have resulted in a dangerous rise of nationalism. Even a part of the left (I mean, socialists who let themselves being swallowed by new regimes), even some communists would have opposed it.
Albania would have been too far away.
Yugoslavia would of course have refused this.
And in East Germany, that would have been really too much for the West, and even for the East Germans.

It was far more efficient to keep formal independence, because the point of "patriotism" worked well to appease some tensions and delay some internal oppositions.

Think about Ceausescu and his nationalism in the 1960s-1970s, which wasn't a real problem for the USSR, but was very efficient to keep a straight control inside the country.

Think about the way Gomulka or Kadar managed to reduce opposition with "patriotic" arguments. Even Jaruzelski used it to justify the martial law.

The only countries where it might have worked for a while: Bulgaria and a separated Slovakia (because not being with the Czechs would have been a small compensation for losing independence).

[big bad fab]

What made them "swallow" the ones they did swallow though?  Were the swallowed ones already more "Russian" at the time?  What is the big difference between say, the Ukraine and Poland?  Latvia and Romania?  Georgia and Hungary?

The answer is: Russian Empire.

Apart from Poland, all the other territories were Russian not long before !

Which territories? You must mean the opposite: apart from Poland none had been Russian.

But then, for that matter, the same was true of Western Ukraine and Eastern Prussia: neither Lviv nor Koenigsburg had ever been part of the Russian Empire.

Yeah, my sentence was unclear, indeed...

You're right for Western Ukraine and you're right it's a good example of what would have occurred in Eastern Europe in case of "swallowing up" by the USSR: armed rebellions.
But, my point was that MOST Ukraine was in the Russian Empire. And, well, even in the Catholic West, the Ukrainian "ethnicity" (I know, it's stupid to call it like that) and common origin made Ukraine far closer to Russia than the Polish territories which were inside the Russian Empire.

As for Eastern Prussia, you can't really say the same: how many Germans left in Königsberg in 1945-46....? Well, the history of this territory "disappeared".

[big bad fab]

Just returnning to previous point.

I would strongly disagree that countries had no autonomy.

After 1956 Poland has the least repressive regime, with Hungary coming very close second.

In 1956 new Polish leadership, in much of USSR displeasure, kicked off stalinist officers from the army and send them back to Moscow, including Marshal Rokosowski.

In 1970/1980 both Gierek and Jaruzelski dealed with opposition, which would be unthinkeable for Moscow comrades.

Yep, and of course, there was Romania.

And Hungary, with Kadar guaranteeing the USSR that there wouldn't be any more revolt and any more independent foreign policy, but gaining some greater autonomy in internal affairs.

And even Bulgaria in the 1950s, with some "troubling" relations with Tito...

And even Czechoslovakia in the 1970s, again with good relations with Yugoslavia (even though that may have been a way for the USSR to "test" indirectly something with a declining Tito).

[big bad fab]

Otto Kuusinen was an example of what would have occurred in the Politburo, had USSR "swallowed up Eastern Europe after WW2"...