Below is a look at the percentage of total world stock market cap that each country's stock market makes up. For each country, we show its percentage of world market cap as of today, as it stood on 9/20 when the S&P 500 made its last all-time high, as it stood on election day 2016, and as it stood 10 years ago.
The US currently makes up 39.81% of world stock market cap, which is more than 30 percentage points more than the next closest country - Japan - at 7.76%.
Note that Japan has moved into second place after being well behind China in November 2016. While the US has gained more than 3 percentage points of global market cap share since Trump was elected, China has lost a significant amount - falling from 10.21% down to 7.54%. At least based on this measure, Trump's trade fight with China has benefited the US at the expense of China.
Hong Kong remarkably makes up 6.75% of world stock market cap, which is well ahead of the UK (4.41%), France (3.14%), Germany (2.83%), and Canada (2.74%).
Since the 9/20 peak for the S&P 500, the US has lost 0.49 percentage points of share, while China, Hong Kong, and Brazil have seen the biggest gains, so things have tightened a little bit between the US and China during the recent sell-off here in the US.