How does he describe the USSR?- He implies the the USSR is keeping "hostage" the various historical cities throughout Eastern Europe. Through Soviet influence and control they are being kept away from the rest of the world.
Why do you think this speech is sometimes considered the "beginning" of the Cold War?- It is probably considered the start of the Cold War because it signifies the first time a major world leader spoke out against the actions of the Soviet Bloc in comparison to the west.