formatting link
"Domestic content data The U.S. federal government uses several approaches to determine the domestic content of vehicles sold in the United States. All of them define "domestic" as a geographic concept, rather than strictly by nation of ownership.For regulating fuel-efficiency, the U.S. Environmental Protection Agency considers a vehicle to be domestic if at least 75% of its content is produced in North America, including Canada and Mexico.
For setting import tariffs, the U.S. Department of Treasury, Customs Service considers a vehicle to be domestic if it has at least 50% U.S. or Canadian content.
For informing consumers, the American Automobile Labeling Act of 1992 (AAIA) considers a vehicle to be domestic if at least 85% of its parts originate in the U.S. or Canada; a part is counted as domestic if at least 70% of its content comes from the U.S. or Canada."