Toyota and Honda saw sales in the US fall sharply in 2011 as production was hit by natural disasters in Japan and Thailand, figures show.
Both carmakers saw sales fall by about 7% during the year compared with 2010.
Their fortunes contrasted sharply with rival Nissan, which saw a strong rise in sales. South Korea's Hyundai also posted much-improved figures.
Overall car sales in the US in 2011 rose by 10% on the previous year, to 12.8 million.
Japanese carmakers have had a tough year in 2011, with both the March earthquake and tsunami, and floods in Thailand affecting production.
The strong yen - which increases the price of exported cars - also put pressure on sales overseas.
Last month, Toyota said it planned to increase production by 20% and sales by a quarter this year as it tries to recover lost ground.
The company is due to lose its crown as the world's biggest carmaker to the US's General Motors.