About half of my coworkers buy food at a restaurant every day for lunch. I can’t speak for the rest of the meals since I grew up in a frugal family and my wife and I are fairly frugal. We still eat out more than I like, which is about 4-5x/month, and I think a lot of people eat out like for half or more of meals.
And the worst part is, people who eat out a ton often go to fast food, which is incredibly unhealthy. We go to fast food maybe once a month, the rest are to more interesting restaurants.
I think the average American will have breakfast cereal or a muffin or donut (i.e. with their coffee) for breakfast, then fast food for lunch, and either fast food or a prepared meal from the grocery store (e.g. freezer section) for dinner. Cooking is a rare thing on weekends or even guests come over, if it happens at all.