German units in France were a reflection of the Italian campaign in progress, and the lack of build up of an invasion force in the UK. Change Allied strategic deployments, and German dispositions will change.
German strategy and intelligence in Western Europe were a mess in 1943 - there were substantial force commitments to NW France, Norway, the Balkans, and Italy all on the basis of defending against potential landings. Italy and the Balkans received the greatest share of forces because that seemed like the most likely followup point from the Tunisian Campaign, not because the Nazis had any particularly insightful intelligence about where the next landing would take place. Even with a buildup for a cross-Channel attack, substantial German forces are going to be spread between the Balkans, Italy, France, Norway, and above all Eastern Europe. Even if all Nazi forces which concentrated in Sicily were deployed to NW Europe instead, we're talking about 2 extra panzer divisions - a drop in the bucket compared to OTL 1944.