What is the difference between the unions of the past from the unions created in the USSR and the USA?

What is the difference between the unions of the past from the unions created in the USSR and the USA? who became an ally of the ussr or the united states?

If we talk about the alliances that have formed around the USSR and the USA, then everything is very simple. The fact is that all alliances around these countries were built on the principle of a political system. Here in the USSR there was socialism and all the countries of the socialist camp united around this country, but all the countries of the capitalist camp united around the United States to create a counterweight. But those alliances that were earlier were created more on a territorial basis in order to jointly defend their territories from enemy attacks.