This is a great question. There are several important factors to consider. First and perhaps the most important reason is that the United States became the most powerful nation in the world. After the fall of the Soviet Union, the United State emerged as the only superpower. For this reason the rest of the world tried to imitate the United States. We were at the top of our cultural power. This also translated into the economy.
Second, the United States also had great companies that emerged. Think of Microsoft, GE, and Apple. This is a point that needs to be underlined. Americans were some of the more ingenious people in the world and we were ahead of the rest of the world in may areas.
Third, part of the standard of living was also false. This is the dark side of the picture. Many people in the last decade borrowed more than they could afford. This is partially why we are in an economic mess.