If you are from America, you might not know that most countries are not too eager to display their flag on their clothes. They would rather keep the flags for places like above the supreme court or government buildings. However, Americans are quite the opposite. They tend to be pretty patriotic and are eager to show that to the world by putting the American flag on all sorts of clothing items.
Some countries might even consider it offensive to put their flag on articles of clothing. While the flag is something to be proud of, it is also something to honor.