I don't like how they encourage picking a doctrine instantly.
Again, why not? It provides more viable options.
I can't be the only person who equips doctrines just so my opponent will be really fucked if he decides to use certain units, am I? (IE if he builds a kubel, I can shit out a jeep and instantly counter it.)
Nothing about 0cp units prevents you from doing this.
I'd much rather the jeep be buildable as a core american t0 unit than be locked behind a doctrine. In general, I'm really not a fan of calling in units that aren't late game tanks or battle groups. I prefer when they have to actually be built at a structure, using up time and a production slot.
Are you arguing that all 0cp units should instead be core units? I'm all for increasing available options but that seems a little too strong to me. You get access to the dodge in exchange for NOT having access to easy eights or paratroopers or whatever.
The variation in American early game is in the decisions to buy upgrades or mix in RE/ambulances. A 2x riflemen 2x RE build has its strengths if you make good use of fighting positions. 3x Riflemen is just the current trend but it's far from the only viable option. (And past 50 fuel, Americans have a ton of great options in terms of tech and units.)
Alright, a few more options. Why not more?