Why do you call America "Uncle Sam"?

It is said that in 18 12, Samuel Wilson, another beef merchant in Troy, new york, USA, became Uncle Sam locally. His initials are US, just like those in the United States. So the residents of Troy took Uncle Sam as the nickname of the United States. In 1930s, cartoonists began to imagine Uncle Sam as an old man. 196 1 year, the U.S. Congress passed a resolution recognizing Uncle Sam as a symbol of the United States.