The question is not whether when this goes hot it will be III, IV or V. The American Revolution was part of WW I. The Great War, the War to End All War, was WW II. The war against Fascism was WW III or WW II continued. The Cold War was no war at all but a series of local wars that involved the US locally. There was never to be a major war between Russia and the US, nor with China. In the next world war Russia, China, and the US will be allied once more.
Sure there was. It was fought largely though espionage, fifth columnists, and infiltration.
There would have been no arms race (or at least it would have been delayed) without spies handing over nuclear secrets.
Our government certainly has been compromised by communists.