I was being facetious. I know how we kept the Russians out of West Berlin, West Germany, Austria, Greece, etc. it was a strong American Military presence and the threat of Nuclear War.
While it was true that the Russians voluntarily gave up some territory in the 90’s it was in exchange for economic cooperation and investment from the West. That cooperation has been squandered but it really was going to be parasitic anyway. It did make some Oligarchs rich.