Not difficult at all. Keep Japan out of World War 2. Scale down the anti Americanism, dont bomb Pearl Harbour, and forget about trying to acquire places like the Philippines, Dutch East Indies, or Indochina. Soon enough, Japan turns into an anti-Soviet anti-Communist ally of America in the vain of OTL Spain and Portugal or an alt-Italy that remains neutral in World War 2. If you add to that deeper involvement in the Far East during the early 20s, you end up with a Japan that holds Korea, Taiwan, Sakhalin, the Russian Far East, the Kurils, Manchuria, parts of China that could include Hainan, etc. The latter may piss off the French, but if the alt-Japan adopts an anti-communist stance in Southeast Asia it may very well gain substantial influence there as well.
Korea is a lot closer to Japan than Angola is to Portugal. Also unlike Angola Korea has only one small and narrow land border. Much harder to smuggle people, weapons, supplies, etc across.While you're obviously right on the type of foreign policy route Japan needs to take, keeping the Empire until the present day is a lot more challenging than that.
You need to find a way to have Korea, Taiwan and Manchuria not revolt.
Portugal was a NATO member and that didn't exactly stop the west from backing anti-colonial guerrillas in Angola...
Korea is a lot closer to Japan than Angola is to Portugal. Also unlike Angola Korea has only one small and narrow land border. Much harder to smuggle people, weapons, supplies, etc across.
While you're obviously right on the type of foreign policy route Japan needs to take, keeping the Empire until the present day is a lot more challenging than that.
You need to find a way to have Korea, Taiwan and Manchuria not revolt.
Portugal was a NATO member and that didn't exactly stop the west from backing anti-colonial guerrillas in Angola...
Still, I think American foreign policy in our timeline also proves that they were willing to go a great distance to prevent communism in Asia. If they were ready to offer hundreds (?) of thousands of American lives in East Asian wars against communism, I'm sure they would be willing to tolerate a lot of Japanese colonialism or even ethnic cleansing in their territories. While you are definitely right in that there are limits to American support, having the Soviet Union as the only alternative right at the doorstep distinguishes Asia from Africa, where Americans supported many non-communist i
Still, I think American foreign policy in our timeline also proves that they were willing to go a great distance to prevent communism in Asia. If they were ready to offer hundreds (?) of thousands of American lives in East Asian wars against communism, I'm sure they would be willing to tolerate a lot of Japanese colonialism or even ethnic cleansing in their territories. While you are definitely right in that there are limits to American support, having the Soviet Union as the only alternative right at the doorstep distinguishes Asia from Africa.
Keeping Taiwan wouldn't be that difficult in a "no Japanese involvement in WW2" scenario. Keeping Korea in such a scenario is a totally different ball of wax. I can't see Japan keeping Korea without lots of protests and reprisals happening which may be enough to get international pressure on Japan to let Korea go.
Also, it would probably have nuclear weapons.A different Japan, that never invades China in 1937 would need Western approval a lot less than Portugal, France, etc did. Because such a one would eventually be able to repair relations with China. A massive trading partner right there.