There is more to it than tax rate percentages, 68 nations worldwide have income tax treaties with the U.S. As an expatriate it is important to be aware of the option available to you under these treaties. Residents (not necessarily citizens) of foreign countries are taxed at a reduced rate, or are exempt from U.S. taxes on certain items of income they receive from sources within the United States. These reduced rates and exemptions vary among countries and specific items of income. Under these same treaties, residents or citizens of the United States are taxed at a reduced rate, or are exempt from foreign taxes, on certain items of income they receive from sources within foreign countries. Most income tax treaties contain what is known as a “saving clause” which prevents a citizen or resident of the United States from using the provisions of a tax treaty in order to avoid taxation of U.S. source income.
Read more at the IRS website: http://www.irs.gov/Businesses/International-Businesses/United-States-Income-Tax-Treaties—A-to-Z Here you can find copies of the treaty agreements, as well.