The U.S. stock market is the largest concentration of wealth in history, and the New York Stock Exchange and Nasdaq together constitute the largest financial market in the world.
Looking at the New York Stock Exchange alone, stocks traded at 7.6 times the value in London in 2018, 3.1 times in Tokyo and 8.3 times in Hong Kong. The U.S. market is also the most traded, which means you have a good chance of finding a buyer or seller of any stock.