First do the trading/gifting -> maybe trading with Greece.
I looked into the save some more:
If we can get medicine, we should build a coal plant in Washington first. The 4 turns for that will be made up by the larger production towards the ToE prebuild.
In the other case a coal plant isn't needed before flight, because cavs are 2 turns already.
War with Japan should start with some gifting. I would gift Ephesus, Pharsalos, Knossos and Thermopylae, but you should prepare first to take all back immediately (and don't forget cities have to be empty).
Ronald has prepared a little for a war with Japan. There are some cavs available. Still you have to play it careful. Japan will have a bunch of ACs already. And there is a road from Sapporo to San Diego.
Klarius' style

would be to capture Sapporo and immediately gift it to China (our probable next target). By that the ACs cannot surprise you, because there is no road within two tiles of our cities they can use. After that you probably can catch the ACs in the open and then push for some interesting targets (Yokohama, Satsuma maybe Kyoto). But the goal of this war is really to get a foothold on still another island down in the south (Hakodate, Shimonoseki, Ise).
There is a small

complication - Matsuayama on the Tatung island. I would pretty much ignore it, except rush one cavalry in Anyang. We have 6 cities on that island, if we should lose one that's no big deal. But again I would rather gift the city to china instead of having it captured.
I really wanted the phony war with China, but this has to wait a bit because we need them to gift cities in an emergency.