Complex sentence: The American upper class is the "top layer" of society in the United States, consisting of those with great wealth and power and may also be referred to as the Capitalist Class or simply as The Rich.
Split into simpler sentences: The American upper class describes the sociological concept pertaining to the "top layer" of society in the United States. This social class is most commonly described as consisting of those with great wealth and power and may also be referred to as the Capitalist Class or simply as The Rich.