Let's suppose for a moment that Stalin does not become GenSec or at least maintain that position for long. Zinoviev or Bukharin ends up succeeding Lenin and leading the USSR during WW2. Their successor is a more pro-democracy member of the Politburo (Preobrazhensky, maybe?), and the Soviet Union begins to politically (but not economically) liberalize; the "fractional dictatorship" is eliminated, much more dissent against the current regime is allowed, etc. Ultimately, you have a more liberal USSR in the post-war era.
Thanks to this, the United States is on much better terms with the USSR. Perhaps even a Wallace presidency in the immediate post-war era.
Obviously, as the Soviet Union and the United States are rival powers, there will be political and economic competition, but in this scenario, it's much more subdued.
My question is: what does America look like without OTL's Cold War? Obviously this would have pretty important effects on internal politics and international policy.