I see what you’re trying to do with these ideas, but you need to be careful or you’ll make the US-China partnership in the game become a penility for the US which wouldnt be fair. Ideas I have heard have been to do things like;
If the burma road is open allow the US to replace the Chinese fighter if it gets destroyed.
If the burma road is open AND the US is at war allow them to purchase 1 unit for the Chinese per turn.
I like both of these and would better represent the US’s support to the Chinese, and also the importance of the Buram road. The second idea would need to be limited to land and air units only (obviously) but to have no more then 1 of each non-infantry/arty unit type (no more then 1 fighter, tatical bobmber, tank, mech infantry, ect…)