I don't know how old you are but I heard this type of statement for over 30 years now and it's just a misunderstanding about what America is all about IMO.
I not an economist so I'll talk more philosophically on this subject. The concentration of wealth or resources is a natural human condition that been happening for thousands of years. This is something you have to accept. America is not immune to this natural law. Being an American does not mean we are all equal and middle class, thats more of a Communist thought process. The ideal of America is to be born equal with equal rights and liberty.
You are not born with the right to be rich, poor, or middle class. You are born with the rights and liberty unencumbered by a government, cast or nobility system to create opportunities to enrich yourself if you choose to whatever degree you choose.