Hi Kelli,
When we came back, I spoke with my vet in the UK about what we needed to do for my cat. She was enormously helpful.
GrnEyes is right that the requirement vary state to state and that the certificate needs to be within ten days of flying. I flew to the US with my cat, so don't know if there are different requirements for dogs.
My vet had gave me the telephone number of the US Dept. of Health, which I called and was actually very helpful. Perhaps if you spoke to your vet in plenty of time, he/she will be able to answer your questions well in advance.
Good luck.