The Germans had 100 divisions fighting the Soviet Union. Had they not been at war with the Soviets, How many of those divisions would have been deployed to the Italian theater. What would the Italian campaign looked like if a large portion of Army Group Center was in Italy instead of Central Russia.
If German troops were in Italy instead of the USSR, no problem - it was their ally. Before they were fighting Stalin, all those German troops were unable to take Britain, and with Italian help, were unable to take even Egypt. They certainly had no way to take Canada, Australia, India, South Africa, British East AND West Africa, British Caribbean possessions, etc. - they couldn’t even take many of FRANCE’S colonies after Paris fell.
Are you counting “Axis” divisions as Germans in the USSR? Plenty of other countries were fighting (and lost heavily) there; don’t include Finns, Hungarians, Romanians, and Italians in those numbers. Germany couldn’t even pacify the Balkans - and don’t overlook the fact that Soviet intervention initially HELPED Germany (the dual invasion of Poland being the most glaring example).