Getting carried away responding to the Russian issue.
If Hitler doesn’t invade Russia he will concentrate on smashing the allied landings in Southern Europe and Sardinia before attacking through Spain or Turkey to get at the allies.
If he doesn’t the Axis will die a slow death.
Agreed on the first point, but what's this abou Spain and Turkey? Hitler hoped that both would eventually join the Axis, and both had non-negligible armies that could be supported easily by the Allies. Of course, that just would put Hitler in worse straits, as more and more troops are tied down in Southern Europe when Stalin launches reverse-Barbarossa...