So, I do know about two other threads about the World War 2320 scenario, but "the boss is your friend" is not helping me.

Here's the thing: I tried this scenario about ten times now. There are three approaches I have tried and all of them failed miserably every single time, so if anyone has any idea what I could do, I would be grateful. Here is what I tried:

1) Confrontation. Try to secure land and fortify, face the boss head-on and defend territory. Obviously failed. Got wiped out by the boss alone.

2) "The boss is your friend". I tried following the boss around with two fields distance. Resulted in him taking back any land I retook before. I could never build up enough army strength to defeat the boss because he craps out stacks of armies at least 10 strong. These constantly combine to stacks 50, 80 or even 110 strong and destroy everything I could build up (there's always at least three of them encircling me). On the rare occasion that this does not happen, at least two other AIs invade from Europe and Asia doing the exact same thing.

3) Flee the continent. It is possible to escape to Europe and take the British Isles or Scandinavia, but in extremely few turns, the boss AI has taken all of America, gets 118 units per turn and crushes me and my maybe 60 or 70 units with several stacks of 80 to 150 units. And no, he has not left for Asia or Europe even one single time.

This is incredibly frustrating and I am extremely close to just quitting this game. I'd keep playing if I could go past that level and just play the others, but no, that one level has to exclude me from all the rest.
(Also, "git gud" responses aren't appreciated.)

yeah. i haven't beaten it either. The single player levels are all hard. Multiplayer is more fun.