Correct answer: The spread of US culture to other parts of the world.
There is a connection also to the idea of America's growing power in the world after World War II, but to talk about "Americanization" refers to the cultural influence and impact of America across the globe, which also began to grow in the second half of the 20th century. British writer Chris Blackhurst described his own feelings as a young man in northern England, where he and his friends thought of Americans as "having greater knowledge and experience – not of politics or world affairs, but fashion, film, music, cars, shopping. We craved to be American." (See article: "How the World Was Won: The Americanization of Everywhere," <em>The Independent, </em>October 2, 2014.)
An example of the spread of Americanization across the world can be seen in the growth of fast-food chain McDonald's. McDonald's was founded in California in the USA in 1948. In the 1960s, McDonald's began opening restaurants in other countries -- Canada and Costa Rica first, and kept going from there. Today McDonald's has 32,000 locations in 117 countries. That's just one example of Americanization -- spreading a menu and food culture worldwide. Other examples from music and movies and the arts could be cited, as well as clothes and cars and many other American trends.
Not everyone views the spread of American culture worldwide as a good thing. Some see it as clouding the cultural heritage of other lands when they fall under US cultural influence.