So after WW1, the USSR has shifted itself on maximum productivity of a suprior naval force. They built battleships, destroyers, carriers, cruisrers, and used all the brains in germany to get all those tech advances: new tanks chassys, tank armours, new guns, projectiles, new engine technology, air land and sea warfare doctrines superior from the old ones due to the new available technology.
Since WW2 never happened, the European demography never collapsed and the US never curled out of their isolation policy, although their economy was booming and their navy was growing too ( from the fear of the Russians )
Now in order to even think about the US, USSR needs a supply base like US had England in 1944.
I propose central America. Massive Soviet convoys would stretch to central america in order to "help" the nicaraguan communist gov fight honduras. The carribean sea has to be controlled by USSR.
Now find some ideas where we can invade an island