Kildee's proposal would provide an additional $4,500 for EVs assembled in U.S. factories represented by a labor union.
Sen. Debbie Stabenow, D-Mich., led an earlier proposal in the Senate that also would tie additional EV tax credits to vehicles assembled in unionized U.S. factories.
"We cannot support any proposal that creates a discriminatory environment in our states by punishing autoworkers and car companies because the workers in their plants chose not to unionize," the governors wrote in the letter.
"By putting certain vehicles at a cost disadvantage, this legislation works against our states, undercuts our residents and negatively impacts the U.S. economy," they wrote. "Congress should not enact proposals that favor vehicles produced by one work force over another, particularly when doing so dramatically limits consumer choice and undermines larger carbon emission reduction goals."
The governors who signed the letter to House Speaker Nancy Pelosi, Minority Leader Kevin McCarty, Senate Majority Leader Chuck Schumer and Minority Leader Mitch McConnell are from Alabama, Arizona, Arkansas, Florida, Georgia, Indiana, Mississippi, Oklahoma, South Carolina, Tennessee and Texas.
Michigan Gov. Gretchen Whitmer, a Democrat, did not sign the letter. Her state is home to the UAW.
The group is urging Congress to "consider the investment and employment created by all automakers — nonunion shops included" as they evaluate the proposals.
The governors' letter comes after a group of more than 100 House Democrats — including Michigan Rep. Debbie Dingell — urged Pelosi this month to keep the union-built provision in the trillion-dollars spending bill.
In September, top U.S. executives from 12 international automakers including Toyota, Honda and Volkswagen pressed House lawmakers to support broader tax credits for EVs in the bill and to oppose "policies that slow progress toward meeting our nation's climate goals."
The American International Automobile Dealers Association, which represents more than 9,000 international-nameplate dealers in the U.S., also urged House leaders to oppose the EV tax credit proposal in a separate letter sent last month.
The UAW, which represents U.S. autoworkers at General Motors, Ford and Stellantis, has urged Congress to pass the reconciliation bill with the "Kildee/Stabenow provision" on EV tax credits.