Midway has often (including as the title of a couple pretty good books) been described as a "miracle" victory. While the U.S. undoubtedly had its fair share of luck, most significantly in the way that the series of entirely uncoordinated airstrikes from both the Atoll itself and from the carriers overstressed the Kido Butai's CAP, the reality is that the entire Operation MI (the overall title of the Midway and Aleutians operations) was a goat rope from the word go. The American victory was much less a miracle and much more an example of bold leadership, proper use of Intel, and a slight, but critical USN advantage in technology (the U.S. had air and sea search radar, the IJN did not, even with the somewhat amateur effort at fighter control, at least the U.S. force knew that there were strikes inbound).This is a hilariously piss-poor recon. So they expected a 3 to edge in numbers, no tanks, and little protection. Instead, they would be the ones outnumbered, be vulnerable in those "please shoot me" rubber boats, and face cannon fire from unexpected sources. And they missed that in a land of 1,200 acres. Heck, even missing them in a plot of land 10 times as big is pretty crappy intel.
Huh, I thought the Aleutians were a logical follow up to a capture of Midway and winning the battle of Midway (of course, here the battle of midway is won, the island is almost untakeable. For reasons I previously mentioned, I don't think it's impossible but less than a 1 in 1000 odds. Since they Americans lost 3 carriers and the Japanese zero, I guess Samoa is next? Also, Henderson Field isn't a great comparison since Midway has bunkers that can withstand 305 mm fire for the men. Presumably fuel, food, and ammo would be there too, although it might be hard to get a plane into the door.
So a siege is not going to happen (well, unless you count seven days as a "siege") and the island is safe. The airmen were also saved and Midway is within ferry range.
Why? In TTL, the Japanese achieved victory by conincidental means (I remember something about submarine pickets and coordination of surface ships and air recon that never really happened, in my OP I said that the nebulous plan worked). In other words, they didn't expect the USN to be there and only found it. In short, the Americans are reading the Japanese like an open book and the Japanese were only able to achieve this thanks to the sub picket. Also as I mentioned earlier, the loss of the flattops isn't that much of a problem if the pilots and planes are saved, and Galveston bay even mentioned a concrete plan.
Yamamoto, for all his acknowledged brilliance, allowed himself to be rushed in laying the missions out, something that compounded by his well established tendency to create overly complex plans, resulted in so many moving parts that MI was a perfect recipe for disaster. As was noted earlier in the thread there are a couple of really good, almost overly detailed, threads in post-1900 where the Battle and the possible outcomes of the Japanese landings are dissected at length. They are probably a couple years old at this point.
In the long run Japan lost the war the second the first bomb cleared its shackle on December 7th.