As a new player, it was mighty discouraging to kill 10 or more units for several turns in a row and find that the Red Army has gotten yet larger every turn! I felt this was too much, at least at the Intermediate difficulty. It felt like I am playing an RPG, not a historical strategy game. But I do appreciate both that 1) AI obviously does need some "cheats" against the human player; and that 2) balancing the AI is a very difficult endeavor.
I guess I will try it one more go without changing any scripts. Perhaps I might do better this time, since I know the game a wee bit better.
Fair enough, yet at the same time it is hard to say just how much of this was bonus units afforded to the AI or other in game factors
For example, the USSR will by default, AI bonus units or not, potentially have a lot of units coming your way. Lend-Lease, ramping up of the industry in the Urals, Industrial Modifier level, Production Technology level, as well as often the ability to rebuild units at 60% of their original cost if they were destroyed in good supply are all factors.
If you still have an original save from your first game you can actually check to see just how many bonus unit events provided to the AI had actually fired, and how many are still on the list relative to when you first start the game. Note the bonus units for the AI are labelled as such, within the last few pages of UNIT events, and not the expected in game unit events that will occur for any game, e.g. AI or multiplayer.
As mentioned the idea really is to smooth out the game so that it doesn't potentially collapse too quickly (at least for the USSR AI bonuses) and there really shouldn't be a wall of units coming your way via the AI bonus scripts. It should be very piecemeal over time and very specific to certain locations and often none at all in those areas if you haven't even advanced far enough.
The other option is to try a game with all the AI USSR bonus scripts disabled just to see what sort of difference you'll experience.
But even this is a bit tricky to know just how much the AI bonus scripts come into play or not, as you have also mentioned that each game will likely be better as you learn the game, learn from mistakes and fine tune your strategies.