What stops them from doing it now? What about Apple being willing to hop in bed with the US government affects whether they would with Russia or China, or whether either of them would ask for this from Apple?
As a multinational company, it's in Apple's interests to maintain a 'no backdoors' strong privacy stance, or it will both lose foreign markets (that are afraid of US/other nation's backdoors) and have to contend with increased requests from various governments for backdoors/audits (they got backdoor access, why can't we?), and the associated revenue lose.
I'm not saying Apple is evil, merely that multinational corporations don't have to care about political boundaries.