Final answer:
American firms lost market dominance in the 1970s and 1980s due to the shift from manufacturing to service industries, increased competition from foreign producers, and reduced desire for unions because of workplace protection laws.
Step-by-step explanation:
The primary reason why American firms lost market dominance in many industries in the 1970s and 1980s was due to a combination of factors. One of the main reasons was the shift from manufacturing to service industries, which resulted in a decline in the competitiveness of American manufacturing firms. Additionally, globalization and increased competition from foreign producers played a significant role in the loss of market dominance.
Another factor was the reduced desire for unions because of workplace protection laws that were implemented during this period. These laws provided workers with certain protections, reducing the need for unions and leading to a decline in their influence and power.