So, when it comes to Arabs, my ideas are to:
Make flamethrower into a bulldozer and *slightly* increase its damage against buildings to give it an actual purpose;
Buff Biotechnology upgrade 3 as it serves nearly no purpose right now, either by making it strenghten Arabs' armor, or shortening the research time;
Buff Arabian WU3: make it increase the speed of half-tracked suspension by 2 (making it even with medium trike), or/and slight armor buff.
While Arabs are weak in late game, they're ridiculously strong in early. Even though Arabs in early are pretty much even to other nations on AB, they have potential to easily crush them on more open maps. Need to be careful not to make their buffs relevant in early game.
Russians need a small tweak, though. Their early is weak, so their odds of survival in 1v1 combat are very slim. But if they survive that early weakness, they become some sort of unstoppable monsters. I think it'd be a good idea to alter space-time technology upgrades:
0: Time lapsers and Tau-radiation a little stronger;
1: Time lapsers and Tau-radiation stronger (something like x1.5 of current #2);
2: Increases the power of teleportation ONLY (make it as strong as it is with tech upgrade 3 now);
3: Slight nerf to time lapsers (not Tau-radiation!)
Also, shortening the teleportation animation would be a very intuitive change.
That would make Russians still vulnerable to early attacks, but they'd have quite interesting scaling scheme: 1st upgrade would allow them to defend themselves just fine, but the 2nd one (assuming they still live to research it) would make it possible for them to somehow counter rocket launcher rushes, making it possible to survive.
No worries about Russians going for time-space 2 instantly - they NEED WU2 to have even a chance of defending themselves. Can't do both by 10:00. If they do - they won't have cranes, thus long enough attack will destroy them anyway.
The time-space 2 change is supposed to make them relevant in 2v2/3v3 games. Well, I'm not sure if it'd be balanced, but sure I'd like to see it!
As for Americans, lasers serve no purpose now. Well, lasers can obliterate same amount of double guns or rocket launchers, but later on will hit an armoury like a brick wall. Even though lasers are cheaper than double guns and rocket launchers, they take longer to make, and require more electricity to produce - laser add-on requires 15 electricity. Producing rocket launchers or guns in factory and researching stuff in 1 laboratory uses up 55 energy. Producing lasers and researching in 1 lab - 65. If you want to power your stuff with solar power plants - you need to build 4 to produce lasers, opposed to 3 when you run more conventional tactics.
Thus, even if you want to beat a large amount of enemy tanks, it's better to do double guns, as it scales better, and you won't be able to produce more lasers than double guns anyway.
My idea is to make laser add-on use 10 electricity instead of 15. That's it.
Sophorific ammo also needs a tweak, but I have no idea how to balance it.