A note on McCarthy... he was a political opportunist who GROSSLY overstated any Soviet sympathizers in the government... the man was a level of trash bordering on being nothing more than a leather sack filled with wet farts.
Was he?
Was he really?
You don't get how pervasive the Communist ideology was.
The key to the man was his nickname: Tail gunner Joe.
He was a lawyer in the Marine corps, he would take joy rides in the rear gun position and blow thru a belt of ammo killing water.. he ran as a war hero.
So yeah he really was a douche bag.
EDIT: Should make it clear he was assigned to a rear area... not a combat unit.
Maybe he was, I don't know, what I do know is McCarthy emerged as a response to the realisation of how completely FDR's administration had been infiltrated by Soviet leaning people. Arguably, China was lost because of their interference that made the complete t**t Chiang look so much worse than the complete t**t Mao. Both were dreadful, Chiang would have been better not only for the West but also for China. I don't say he would have been good, but I do say he would have resulted in fewer dead Chinese people and speaking of Vietnam, no safe rear area for the Viet Minh/Cong to retreat to.
McCarthy was part of a group of people that thought "Ike" was a communist, same group of people that took out a full page "wanted dead or alive" poster for JFK in Dallas... and that group is the one that had and has pushed the narrative you refer to.
https://link.springer.com/chapter/10.1057/9780230616257_7?noAccess=true. An interesting confluence of the right and left in blaming FDR but for different reasons: The right he was to left leaning (Note that their same financial backers of the accusers also backed a pro fascist coup against Roosevelt in the 30's)... and the left because he refused to shift support from Chiang to Mao, or have anything to do with Mao. Will include a footnote or two from the link here:
Report by Currie to Roosevelt, March 15, 1941, box 427 Roosevelt Papers; Visit to China of Lauchlin Currie file, March 3, 1941, DOS, Decimal File, 003.1193, RG 59; Currie to Roosevelt, ibid. Following up on Currie’s recommendation, the United States sent both a military and a civilian advisory mission to China to address transportation, currency, and military supply issues. The State Department also dispatched Owen Lattimore, an academic specialist on Asia, as a political advisor to Chiang.
As with later American emissaries, they were largely ignored. By the late-1940s, Currie was accused of being a Soviet sympathizer or even spy. Although never charged, he left the United States.
At least through early 1944, Currie was among Chiang’s most ardent supporters in Roosevelt’s inner circle, not an advocate for the Communists.Google Scholar
Daily diary entry of November 4, 1944, Stilwell Papers; Roosevelt to Hurley, October 14, 1944, box 88, folder 8, Hurley Papers; Hurley to Roosevelt, October 15, 1944, ibid.; Roosevelt to Chiang, via Hurley, October 18, 1944, ibid.; entry of November 3, 1944, vol. 48, Stimson Papers.
Hurley was a flamboyant egotist and later a raving reactionary. Many Amerians who met him in China in 1944–1945 also thought he was mentally unstable. See the discussion in MacKinnon, et Al., China Reporting.
So we have a mentally unstable raving reactionary hurling accusations... that are not born out by objective reality.
The major reason the US never invaded the North was to not trigger the million Chinese pouring across the border response seen in Korea.... hard to make the case that the democrats were a bunch of commie sympathizers when they went to war in Korea and Vietnam to prevent communist expansion at substantial political cost to their party. Also it was the Democrats pushing Nixon to use US air power to assist the Republic of South Vietnam AS THEY HAD PREVIOUSLY GIVEN BLANKET AUTHORIZATION to do in holding off the NVA.... they also never, EVER stopped paying the bills, the last authorization was for half what Nixon sent to congress but was also twice what was actually expended by ARVN in the prior year.
It is worth noting that Nixon had been leaning on the ARVN to expend less ammunition for the prior 3 years, which they complied with, and then sending budget requests that were inflated in comparison: The last authorization IIRC was four times the amount of expended ordinance and the Democrats wrote a check for half that.. so twice what ARVN expended.
EDIT: I am the one who added the bold to the foot notes... usually I am to lazy to even attempt to use the cool board features.