I'm by no means a historian, but...

With Mussolini still rising to power in Italy, fascism has a diminished role in Europe, until the Spanish Civil War. With less on the line, it seems more likely that the European powers would see a bigger interest in helping Franco crush the Communists, leading to the UK and France sending aid to Franco's side along with Italy.

The USSR continues to aid the Spanish communists, but perhaps becomes more aggressive in their aid due to the involvement of the other European powers. Tensions rise in Europe, the USA continues to pledge neutrality (but likely funnels money/non-military support to Franco.)

Regardless of which side wins (Franco or the Communists), the USSR continues to feel an increased need to expand its sphere of influence in Europe. Tension continue to rise until eventually one of the European powers, or Stalin, makes the first move...and then we have World War II, but with the USSR against the traditional European allies.

That seems the most likely scenario.

Unfortunately, AskHistorians only deals with what did happen, not what might have happened and I've therefore had to remove your post. However, your question would be perfect for /r/HistoricalWhatIf, should you wish to cross-post.

Thank you.