The US – it is impossible for any country to attack them without a navy. If Japan wants to attack the US with a sizeable force, it’s going to take at least three turns, and the US can easily defend, making such action unreasonable. Meanwhile, the US can take the Canadian territories pretty easily from the British, move all their navy into the Atlantic, and go into Africa, possibly with an IC in Brazil. The British will slowly have their IPCs taken away by the Japanese in Asia and the Southeast Pacific, and should pose no threat to the US’s landgrabbing in Africa. The US is better positioned to exploit Africa than the Germans, who have to concentrate their IPCs on Russia, while the US has no country to attack it via land. For the Japanese, it would be unreasonable to think of attacking the US when such an attack is doomed to failure, and there are many poorly defended territories in Asia for Japan to exploit. Germany will be focusing its efforts mostly on Russia, and possibly Britain. However, they cannot build a sizeable navy for a couple of turns, by which time the US navy will dwarf its German counterpart, and stop any action in Africa. Once Germany and Japan destroy Russia, they will start fighting amongst themselves, while the US can just wait until the most oppurtune moment to strike.