The answer lies in the returns, composition, and size of U.S. claims and liabilities. As I mentioned earlier, for most cross-border assets, including debt and equity, the income component of the return paid on U.S. liabilities is roughly equal to that received on claims.
The return received on U.S. direct investment claims on the rest of the world, however, is much larger than that paid by the United States on its direct investment liabilities to the rest of the world or on any other asset. Additionally, direct investment is a greater share of U.S. claims than it is of U.S. liabilities.