Of course, the flip-side is that if the West had stayed out, Russia would have been easily destroyed by Nazi Germany.
I, personally, view WWII as the War to Save Communism. Hitler and Mussolini did not spring to life on a vacuum. Fascism was Europe’s response to the Russian Revolution of 1917. A lot of people realized they didn’t like the idea of waking up to their throats being slit.
In a sense, you are right that Hitler probably wouldn’t have stopped with Russia, and the West would have faced a much more formidable adversary.
But the cost of how it went down was the Soviet Union. I wonder how different the results would have been.
Both World Wars, should have just be reduced to fighting between Germany, Russia and Japan.