All societies differentiate between male and female, but one way Americans are unique in how we do it is that we link gender to:

Answer: Colors.

Explanation:

Until the mid-19th century, American children used to wear white dresses regardless of their gender, because white clothes were easier to be bleached when dirty. Then pastel colors for baby clothes arrived, but they were still not gender-specific. It wasn't until the 1940s that producers decided pink was for girls and blue for boys. Therefore, Baby Boomers were the first generation to be raised wearing distinct gender colors.