I think few people would approve of the killing of Native Americans and keeping slaves — now or in 1930s. Some would, but fortunately they are not the political mainstream.
Slavery was abolished in the US in 1865, and in Russia, in 1861, so they had uniquely close positions in this regard. By 1980s, the difference between USA and USSR was far more pronounced, and not in favor of USSR. Maybe the American way was less perilous.
But looking at the American problems of today (the list is long and grave) I can only conclude that there's no silver bullet. We humans are not ideal, you know. OTOH they say that creation of Eden on Earth is a futile task, and we're in a business of keeping Earth from becoming Hell. With this regard, the Soviet way seems clearly inferior.