This depends if your horse is gelding, mare or stallion.
Geldings stay in quarentine for 3 days once they arrive to the USA. You cannot see them but their stay in quaretine is short. They stay in their box for the 3 days.
Mares and Stallions stay 3 days in quarentine and then need to go to special quarentine facilities where you can, walk, lounge and ride.
Mares stay around 15 days and stallions around 36 days.