China and the US have the same life expectancy of 79 years, which is a very recent phenomenon due to the 2005-2018 changes I mentioned earlier. Obesity, lack of exercise and other cultural factors weigh down the US life expectancy compared to all other Western nations. China's use of abortion during the one child policy era also prevented a lot of people who would have had chronic medical conditions and disabilities from being born.
It is not yet true, however, that Americans are getting "less old", though it may soon depending on how China manages it's own growing obesity problem and tobacco use.
