i do believe all are the same in real life. They just hide it. It´s their nature.
I don't think so. At least USA was not emphasized on agriculture as much as China in the past while China was biasing towards males cuz China thought women purely as 'fertilizable walking containers' and their life missions were just reproducing, and males can integrate themselve into the labor power for the agriculture so women's status was very inferior back then.
I don't think USA has such notorious history. USA prospected from advanced scientific researching institutes, educations, nearly complete isolations from World Wars, etc. to the strongest country all over the world. USA didn't use the same expedient as China's to develop itself. So the sex ratio in USA is relatively balanced, not like China, as well as the fact that USA's involution is not as severe as that in China.