According to the Centers for Disease Control and Protection, so far no local mosquito-borne Zika virus disease cases have been reported in the U.S., travel-associated cases have been reported in nearly every state in the nation. In fact, the CDC speculates that "the number of Zika cases among travelers visiting or returning to the United States will likely increase."
If someone who traveled to a Zika area and was bit by a Zika-carrying misquito they could bring the disease with them stateside, where it could spread via additional misquito-bites or sexual transmission (which has recently been confirmed).
Travel-associated Zika virus disease cases reported: 426
Locally acquired vector-borne cases reported: 0
Sexually transmitted: 8
Guillain-Barré syndrome: 1
So how frightened should you be about possible Zika transmission? (Find out here).