The increase to 25% from 15% sent European carmakers down about 2% on Monday after the White House linked the move to Brussels' delayed approval of tariff cuts on US industrial goods.
Bernstein Research said the higher duties could cut automakers' earnings by 9% to 21% this year and 11% to 21% next year.
Earlier, the EU said it wanted trade talks with Washington but was ready to respond and consider all options if the threatened car and truck tariffs are implemented.
How will Europe’s new legislative safeguards counter the threatened 25% US auto tariffs?
Beyond car prices, what are the biggest risks of a US-EU trade war to the global economy?
Are auto imports truly a national security risk or a tool to bypass existing trade deals?