That would be why the US Justice department is looking at an antitrust suit, Anti-trust is the remedy that came about in 1890 when the Standard Oil trust seemed unstoppable.
That said, I see this sort of thing a bit differently.
If Google is all powerful and a monopoly and never in danger of being killed, why comply with an authoritarian foreign nation to remove comments that are amplifying an anti-government sentiment? Why should Google care if the government of China is feeling a bit insecure about their own population's loyalty?
I worked at Google during "China Debacle #1", where Google went to China as an uncensored search engine, left in the middle of China Debacle #2, when China infiltrated Google's infrastructure to use it to track dissidents, and watched from the outside (as many here did) for China Debacle #3, when Google tried to create a censored search engine for China.
Why does Google need China so badly, that they are willing to compromise their values (debacle #3 and this comment censoring behavior)?
I don't think you need the antitrust legislation. I think Google is slowly dying and as they die their ideals wash away. Clean user experience, gone, Useful free services with return only positive feelings for the brand, gone. Employee perks, fading away. Lofty slogans of not being evil, gone.
This compliance, sometimes forced by edict in the EU's antitrust case, sometimes forced by coercion, tells me that Google isn't powerful, it is weak. It has lost its way and may not survive if it is unable to find its way back to something good.