No, that is not how it was introduced to the US.The CDC also now screens new dogs entering the country for the disease and the dogs can also be tested before import. But let's not let facts get in the way of some good old-fashioned dog torture.

Canine influenza H3N8 viruses originated in horses, spread to dogs, and can now spread between dogs. H3N8 equine influenza (horse flu) viruses have been known to exist in horses for more than 40 years. In 2004, cases of an unknown respiratory illness in dogs (initially greyhounds) were reported in the United States. An investigation showed that this respiratory illness was caused by equine influenza A(H3N8) viruses. Scientists believe this virus jumped species (from horses to dogs) and has adapted to cause illness in dogs and spread among dogs, especially those housed in kennels and shelters.