Uhh, let's unpack this.
The CIA tried to kill Castro, back in the days of yore when the CIA actually fought for American interests.
The US put nukes in Turkey, but that's hardly surrounding the USSR. The short range tactical nukes we had in western Europe would not have reached the USSR. The first European based nuke deployment capable of that were the Pershing missiles that Reagan put in Europe in the 80's, over the huge protests of various leftist groups who were funded by the Russians.
For Berlin, Truman merely ordered an airlift of supplies when the Russians closed off road and rail access. Kennedy did nothing when East Germany closed off East Berlin from West Berlin. Our only "threats" were that we would treat an invasion of West Berlin as an invasion of NATO itself, as we should have, as West Berlin was part of the Western area of operation.
When North Korea invaded the South, not sure what else Truman could have done except help S Korea. Also remember the Truman and LBJ wing of the Democrat party is far removed from the current Commie Bernie Sanders (who honeymooned in the Soviet Union, or Alexandra Occasionally Coherent.
If the Democrat party wanted to run someone with the same polices as JFK I might vote for him. But those polices would be considered extreme right wing positions today.