Last first, most world governments get bombarded from space during the 'blue fleet pounds everyone until the remaining mecha corps of all sides band together for survival' stage. Since China was a US ally at this time, the only way you'd get to kill Mao is if he's a collaborationist leader during the 'retake the earth' stage after that. Note that I am actually in favor of such a thing if it can be justified, but as I am not in fact a history buff most of your questions let alone answers will go right over
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"Anko, what you do in your free time is your own choice. Use it wisely. And if you do not use it wisely, make sure you thoroughly enjoy whatever unwise thing you are doing." - HymnOfRagnorok as Orochimaru at SpaceBattles
woot Med. Eng., verb, 1st & 3rd pers. prsnt. sg. know, knows
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"Anko, what you do in your free time is your own choice. Use it wisely. And if you do not use it wisely, make sure you thoroughly enjoy whatever unwise thing you are doing." - HymnOfRagnorok as Orochimaru at SpaceBattles
woot Med. Eng., verb, 1st & 3rd pers. prsnt. sg. know, knows