Because it’s poor - China’s GDP per capita is the lowest among the large economies and thus with capital formation and technological catch-up, China would grow faster than anyone else. China, however, is growing substantially slower than other Asian economies at the same gdppc and substantially slower than its previous self (and China is growing so slowly that there is now deflation and 4% y/y growth, making China positively Latin American)
Simple: America is large because it has been on the technological frontier for a century and has a completely serene political environment. The current account/trade account is equal to (savings - investment) + (taxes - government spending) -
and since the U.S. has been so wealthy for so long, households spend money easily and don’t save precautionarily. This, coupled with endless economic growth in the U.S. means there are boundless investment opportunities for U.S. firms and thus, both low savings and high investments push the current account into deficit.
