This makes no sense. First, holding North Africa didn't even stop an amphibious assault of North Africa, let alone anywhere else. And nobody besides Churchill was even foolish enough to want to get involved in Mediterranean operations. And holding Southern France, Italy, and Greece wasn't a concern of Germany in '41, the Soviet Union was.Beg to disagree, holding North Africa secured all Southern Europe from assault (south France, Italy and Greece).
The other fact is that we are talking about a two year period between the arrival of the first Germans - March 1941 - and the defeat in Tunisia - May 1943.
Second, Germany never held North Africa, they didn't even really try. Their early expeditionary force, the DAK, was simply to help the Italians in Libya who were being embarrassed by the British. Rommel massively expanded the conflict far beyond his mandate and orders, using success as an encouragement to chase the British further east to the point he even got Hitler on board (though not Halder or the OKW , who were not happy trying to supply Rommel's constant requests for more of everything). They only strengthened their forces in North Africa when it became apparent it had become a major theater after Torch had happened (which the Wehrmacht could not prevent). After that to survive they needed to either immediately evacuate (and with it the appearance of weakness) or reinforce failure. They chose the latter.
Overall the ONLY REASON Germany was involved in North Africa had nothing to do with its strategic location and everything to do with saving an ally from humiliation, an ally Hitler wanted to help. Had Italian forces not had great difficulty against the British, not a single German soldier would have been deployed there.