No, it wasn't. Hiss, the Rosenbergs, and so forth were examples of traitors, but there was no real take-over attempt. Furthermore, McCarthy was a vulgar demagogue that liked to play loose with the exact nature of the threat. On top of that, the John Birch society implicated the President of the United States Eisenhower as being a card-carrying communist. You don't get any more ridiculous than that.
The idea that there was no worldwide take over attempt by Communists must certainly be laughed at, positing that they were not trying to undermine our government in myriad ways is also comical.
If you are talking a complete take over of the US...they were not on the verge but they certainly did have many people in key places almost all the way up to the top, besides the previously mentioned
Hiss and
Rosenbergs, then there was
Harry Dexter White, our main man at the extremely influential Bretton Woods Conference, the developer of the International Monetary Fund as well as the World Bank [ not insubstantial, extremely impactful ], many questions about
Henry Wallace, FDR's VP prior to Truman,
Lauchlin Currie,White House economic adviser to President Franklin Roosevelt, director of World Bank mission to Colombia,
J. Robert Oppenheimer,
Theodore Hall, Manhattan Project physicist who gave plutonium purification secrets to Soviet intelligence,
Nathan Silvermaster, U.S. War Production Board economist and head of a major ring of spies in the U.S. government,
Samuel Rodman, United Nations Relief and Rehabilitation Administration and spy,
Harold Glasser, U.S. Treasury Dept. economist, United Nations Relief and Rehabilitation Administration spokesman,
Laurence Duggan, Head of the South American desk US Department of State...
Those are just a few of the many that we now know of... the list is truly long and getting longer with more information obtained after the collapse of the former Soviet Union.
The fact that we had HUAC and McCarthy, just goes to show you it was not just some completely whacky group of far out conspiratorialists that should have been wearing tin foil caps who were thinking along these same lines...the fact of the matter was that Truman was sufficiently concerned with the potential of the problem that instituted loyalty oaths and background checks. He was apprehensive about Soviet subversive penetration and infiltration into the United States government by American citizens who held oaths of allegiance to a foreign power during war time. These US loyalty oaths and background investigations were on persons deemed suspect of holding party membership in organizations that advocated violent and anti-democratic programs...
While vilified by the left, the JBS was mainly for local discussion groups and issued pamphlets warning of the threat of communism. Almost all groups have made individually ill advised or imprudent statements at some time or other. Ike being one of my favorite presidents certainly gives one pause... but the facts were that the Communists had turned some pretty high ranking folks in our government, they were intent on infiltration, were trying to subvert and had made very major in roads... its undeniable except to those who enjoy denying something truthful that they just do not like...