The idea is that if everyone plays by the free market rules, the average country will be better off. If every country plays by these rules except one, which us

The idea is that if everyone plays by the free market rules, the average country will be better off. If every country plays by these rules except one, which uses mercantilist tactics to win zero sum games, that one country will have an advantage. If every country plays by mercantilist rules, that advantage will not be there for everyone, since now the game has changed. China's "unprecedented" growth was achieved by Japan and Korea during their peak growth period. Britain was the original champion of liberalization while the US was protectionist for much of its history. The EU is still quite a bit richer than China and has done well during this liberal period since nearly destroying itself in WW2. There are so many details you are choosing to ignore.