Why not. By what official authority? By what record? Were you alive then? By the 1950s Stalin's regime was our arch-enemy.
At that time China was not the independant power that it has become, the Soviet Communist Party under Stalin controlled ALL Communist leaders, including Mao and Kim Il Sung. Stalin was the Capo di Tuti Capi of the entire communist bloc, and by the 1950s his regime was viewed by Americans as tantamount to Hitler's regime. Our wartime alliance with the Russians ended, and the Cold War began shortly after the end of WW2. In 1948, Stalin cordoned off Berlin, trying to starve out the parts of the city controlled by the allies, resulting in the Berlin Airlift, resulting a year later in the establishment of NATO to counter the Soviet threat.
By the Time the Rosenburgs were fried in 1953, the Soviets were well established as our official Number 1 enemy on the face of the earth, and the prospect of them getting the A-Bomb was our Number 1 fear. The Rosenburgs were most CERTAINLY not spying for an "ally".
Oh, BTW, "police action" was a convenient term somebody thought up at the time to describe a war that had not been declared war by Congress.
Korea was a real war. We thought of it as a real war. And the Koreans and Chinese were part of what was called the Soviet "Satellite System", under the direct control of Stalin.