So I played a few single player games lately. Once as Australia, once as Canada and once as the USA. In short, the western allies AI are completely brain dead. I also played as Germany to confirm if they acted differently when an axis player was present. I know it's kind of a problem in vanilla HOI IV but it is way worst in BICE.

Africa:
The only thing they do is beat the axis in east and north Africa. Always winning quickly against Italy without any help from the player. Most of the time the African theatre is closed as soon as 1940-1941. This is a big problem because they don't do anything else for the rest of the war.

Naval:
The Allies are completely incompetent at defending their convoys against u-boat or Japanese subs. All of their countries loose countless soldiers to subs as they keep sending troops at sea with zero escorts. The US AI don't even try to beat the Japanese fleet and goes no further than wake Island and the Marshals islands in the pacific. Resulting in the Japanese fleet being dominant in the east indies.

Free France Tree:
The free France tree for the allies is a great idea in my opinion, but in single player the allies often block themselves with it. In all of my play-through, at some point an allied nation would research the reunion island political focus. Which is okay... but they wouldn't invade the island afterwards. Meaning that no other focus can be researched in the Free France tree until the player sends an invasion force himself. At my second and third play-trough I knew this would happen, so I was prepared to invade the island as soon as it was researched. It went well we could continue the tree. but eventually after Syria was invaded and surrendered, for some reason the tree was blocked again as if we where still at war with a french colony.

D-Day Tree:
So the AI allies will only start researching focus in this tree in late 1945... Yeah, unless the player start researching all the focus by himself no preparation for D-Day will be made before the war is supposed to be over. Bigger problem is that some of those focused are locked to certain nations, like training in Britain must be done by the UK. By the time they decided to research it, we were in 1946 and the USSR had capitulated.

Without the free France and d-day tree completed the AI stays passive (never try to invade Sicily, Italy and never try to d-day. Even in the pacific the USA don't go any further than the marshals islands. Playing as the allies in single player is completely broken. Even in multiplayer you are forced to have someone playing as the UK and the USA.