FACT: You can still vote in governmental elections in the U.S. 即使你在国外!
It does take some advanced planning but it is more important than ever that we all exercise our right to vote so check out the links below that will walk you through the steps.
http://www.votefromabroad.org/elections/TX
http://travel.state.gov/content/travel/en/international-travel/while-abroad/voting.html