I agree that great power horse trading before and after WW1 has caused a lot of issues. A rules based world order is an improvement on that. I wish USA followed the rules and did not invade nations such as Iraq.
I forgot to mention relative GDP is a bad measure. Absolute GDP (on a log scale) is a much better measure. The relative GDP graph will falsely make it look like India and China declined far worse than they did around 200 years ago. The reason is the industrial revolutions, which separated population size from a nation's GDP (at least until recent globalization). One nation growing due to industrial revolution by itself does not make a stagnating non industrial economy weaker in absolute terms.
I think a large fraction of that relative decline would have happened even if there was not an absolute decline due to misdeeds of certain British and American people in the 1800s.
Industrial revolution works even better if all prevailing exporters all of a sudden fall off a cliff.
"Mean reversion", word of the century.
Interesting bonus fact for economic historians, in 1890, 30% of Britain's GDP was illegal opium smuggling to China.
Would be interesting to see the numbers for the USA (by some accounts, the biggest exporter by that point)...
Courtesy of Aaron Swartz: https://www.jstor.org/stable/3112527
Many historians believe reversal of this treaty caused Pearl Harbor and started WW2.
Quite embarassing for the Nobel Prize winning Roosevelts indeed.
https://www.c-span.org/video/?290682-1/the-imperial-cruise
Most people don't know history, so it's easy to sweep under the rug.