What no one is talks about is outside of US all the countries depreciate their continuously which leads to higher returns in their markets. Problem is if US investors go and invest in these markets, and when they take out their money and bring back to dollars, they will suffer a huge loss because the currency keeps on depreciating and the returns those markets are making are not enough. For example if a outside us Market makes 16% return and depreciated their currency by 6% then you only made 10% when you got your money back in dollars. So compare the returns in dollar terms not in their own currencies.
If we compare in dollar terms, people will find that US markets have continuously outperformed every year as compared to other markets. That is why if you look at the total world stock market you will find 67 to 70% allocation to US markets and 30% outside US . There is a reason for this.
Currency depreciation .
Now US is also on the same path starting depreciating their currency to increase the returns
Edit: Those who are crying about dollar depreciation and thinking outside markets are better are forgetting that this outperform of other markets in other terms has only happened this year. Once the tariff dust settles capital is only going to come back to US