If the Mitrokhin archive is to be believed, the KGB actually had very little success planting their own agents in the US...America was so different from the Soviet world—or even Western Europe—as to be akin to another planet. Some were caught, some cracked under the cognitive dissonance...many accomplished little if anything.
Initially they had great success in recruiting “ideological” spies in the US (e.g. the Rosenbergs and Oppenheimer), but after the depredations of Stalin were revealed to the world in the 1950s, that supply dried up. They eventually found replacement success by seeking people with access to desirable information, who had an inflated sense of self and an ax to grind against their employer.
BITD, Russians would come here and love it so much they wanted to be Americans. The same went for the Chinese. Now the Communist Chinese Party, places keeps family members back under their thumb for leverage.