Answer:
The main effect of the U.S participation in the global economy is that it influences the world economy like no other country, simply because it is the largest economy in the world by a wide margin (the second largest economy, China, is still a few years behind from catching up with the U.S.).
For example, the most used currency in the world is the U.S. dollar, many countries have the U.S. as their most important trade partner (for example, Mexico), and when the U.S. economy enters a recession, the rest of the world feels the effects, as it happened during the 2007-2008 financial crisis.