Ok, I have to ask where we have gotten to in this thought experiment?
We look to be spending time with thoughts of the B-36 making it's combat debut (and what a debut), armed with nukes and hitting Europe either from the CONUS, Iceland, or the Azores? My thinking is that even 2 years ahead of OTL, we are not really seeing them before late 1946. So, we get to war in late 1941, all of 1942 is spent with no US major landings, just the islands campaigns, and then where do we go from there?
I think that the logical choice, given that we know the B-36 is on the way sometime down the road, is to ask ourselves do we risk a landing on the Continent (European one, that is), or do we push across N. Africa, getting bloddied more than in OTL without UK taking up Axis forces to the east, so more than OTL facing the US landings in 1943 NW Africa. Hence, we get bloodied worse than OTL, and progress less rapidly. OTOH, we would at least be fighting the Axis at the end of their logistal string, so if we decided to establish ourselves first, perhaps for all of 1943 without attempting to push forward with green troops against battle tested veterans, we could give the Axis time to overcommit themselves in an attempt to overwhelm the US forces.
If such took place, then once our buildup was sufficient to push forward, airstrikes on ports, convoys, roads and supply depots, withheld (mostly) up to this point, hoping to conceal how much damage such bombing could do, and to make the Axis think that bringing more and more and ever more troops to Africa is the way to go, then we can take out a good chunck of their ground forces as they end up without sufficient supplies to continue fighting. They then would be forced back and out of Africa, and this then gives the US airforces bases sufficiently close to begin plastering southern Italy (with fighter escorts) and softening them up for invasion.
As we were not able to land in Europe historically until mid 1944, and that was with the UK as a staging area and major industrialized population close by and in support, which we lack here, and not really taking much into consideration of how much more difficult the supply of our own troops is going to be lacking that, not to mention the far easier time the Axis have with just a single front in western N Africa, does it seem reasonable to conclude that ITTL, our war might end with a few demonstration raids, in 1945 or early 1946, and their be no need to actually invade Europe if the mushroom farms start sprouting? Basically, would the Axis hold us back sufficiently for the B-36 to even play a roll? Or would it just arrive a bit to late even in TTL?