Final answer:
As of 2012, Toyota was the world's most valuable car company, based on Fortune Global 500 rankings. American car companies like GM, Ford, and Chrysler faced tough global competition, leading to increased innovation and improved quality in the U.S. automobile industry.
Step-by-step explanation:
Based on 2012 rankings of Fortune Global 500 companies, the world's most valuable car company was Toyota. Globalization has broadened the playing field for many industries, including the automobile industry. U.S. carmakers like General Motors (GM), Ford, and Chrysler once dominated the market but eventually faced intense competition from foreign automakers. This competition led to innovation and a significant rise in quality for American vehicles. While in the 1970s, U.S. auto production was marked by complacency, by 2007 these three firms accounted for less than half of U.S. auto sales, emphasizing the shift in market dominance and the impact of global competitors such as Toyota, Honda, and Nissan.