Yes, international investors owe tax on income derived from U.S. real estate. However, foreign investors are taxed at different tax brackets than U.S. persons and do not qualify for the same capital gains rates enjoyed by U.S. citizens or permanent residents.
Per IRS rules, rental income from real estate owned by a foreign investor is taxable at a flat rate of 30%, unless your country of citizenship has a tax treaty with the United States or you own real estate in the United States “in connection with a U.S. trade or business”.
For further reading, see the IRS’ page on FDAP income.