Originally Posted by sammyk

According to this you have to be 18, not 21 to drive in Texas with a foreign license provided there is reciprocity between the two countries.

Texas DPS

1) How long can I drive with an out-of-country driver license?

Generally, a person 18 to 75 years of age with a valid out-of-country driver license in their possession may drive a private, non-commercial motor vehicle in the State of Texas for up to one year from date of entry into the United States, if their home country has reciprocity with the U.S.