Landing craft is NOT an issue. If you read "1943: The Victory That Never Was," or even if you just do the math, you will realize this.
The Allies had enough landing craft to land SEVEN divisions in Sicily in 1943. These were slated to go back to England in time for Sledgehammer in late summer 1943. However, since Alan Brooke was so CHICKEN about landing in France in 1943, the U.S. Navy took all the landing craft off into the Pacific. If that hadn't happened, there would have been LOTS of landing craft of all types available in 1943.
I think the best scenario would have been if the French government had evacuated everything they could have to North Africa, as I recently posted in The Turning Point. With the French navy and allied French troops in Tunisia, Libya and the Italian empire in Africa would not have lasted long enough for Rommel to even be dispatched. The Mediterranean would have been a British/French lake and Malta would have been safe.
Also, remember the Reuben James. This sinking happened because Roosevelt was pushing for more and more active action by the U.S. Navy in the Atlantic. The RJ was the third U.S. destroyer to be torpedoed, because Roosevelt had the U.S. Navy actively convoying all Allied ships in the Atlantic, with orders to shoot German units on sight. FDR knew that Germany was the main problem for the Allies, and since Sept 1939 he had been looking for any provocative incident that would get the U.S. electorate behind him and into the war in Europe. If there had been one more incident like the RJ, one of two things would have happened: Hitler would have declared war on the U.S., or the U.S. would have declared war on Germany.
The main stumbling block to a successful landing in France in 1943 would have been the lack of training and proper equipment. Training has been covered above, so we'll just mention the equipment. Specifically, many of the armoured units of the U.S. Army were still equiped with things like the M-3 Medium Tank (the Lee-Grant) or the M-4 early, poorly-armoured version of the Sherman, while the main British tank was still officially the Crusader (They were just starting to introduce the Cromwell.) Up against the PzKw IV Gs, Panthers and Tigers of the Wehrmacht, they would have been slaughtered.