The Japanese beetle came to the U.S. east coast in 1916 on a shipment of iris bulbs. They have slowly been working there way westward.
Check out the text below. This comes from a Oregon Department of Agriculture site.
Japanese beetle adults are active flyers and frequently fly short distances between plants. The beetle is capable of flying up to five miles with the help of the wind. Natural spread by flying adults will gradually expand the beetle’s distribution in the U.S. Long distance expansion and new introductions are usually aided by commercial activities. Grubs are easily transported long distances as hitchhikers on shipments of plant material usually associated with roots and soil. Adults may be carried in planes, trains, or automobiles to uninfested areas. The Oregon Department of Agriculture (ODA) routinely inspects cargo airplanes arriving from infested areas during the adult flight season. Isolated infestations of the Japanese beetle have been found in California, Colorado, Idaho, Montana, Oregon, and Utah.
https://www.oregon.gov/ODA/shared/Documents/Publications/IPPM/JapaneseBeetleFactSheet.pdf