Yeah, the NY times article[1] actually says it was the US embassy in France that requested it was banned "on the grounds it might assist Communist propaganda efforts".

The last paragraph says:

"The Russians managed to obtain a print of "Grapes of Wrath" and displayed it widely behind the Iron Curtain hoping to convey a harsh impression of the US. But the main reaction, reported by our embassies, was: "In America even the tramps have cars."

[1]: https://www.nytimes.com/1955/04/13/archives/foreign-affairs-...