Below is a link to the UGA beekeeping newsletter that states AHB are officially in FL -- Tampa area to be specific. They think they arrived not by eastward migration, but by ships or even brought in on purpose.
According to the State of FL, AHB swarms were intercepted 30 times in the past 22 years mostly on ships coming from Guatemala.
On a lighter note, there is a petition afoot to get a honeybee stamp. Here's a link.