What are common heritage of American people?

There is no specific common heritage of American (USA) people.

The US has native, or indigenous, pre-Columbian Americans, called Indians by fifteenth-sixteenth century explorer, Christopher Columbus, who believed on arriving in the Americas that he'd landed in the East Indies, a part of Asia (later, having worked out America wasn't Asia at all, the name was changed to West Indies, which is still used in the Caribbean). Today we refer to specific countries, or use the term New World (as opposed to Old World, usually seen as Europe). The word, America, has Germanic origins.

In the nineteenth century native Americans were called 'red' Indians to distinguish them from Indians inhabiting the sub-continent, India. Native Americans are thought to have migrated to America from Eurasia more than ten thousand years ago.

Apart from native Americans, the population of the US is comprised of immigrants from pretty well every part of the world. Just have a look at your local telephone directory and check out the surnames!

Some Americans might share a common heritage, but as in other countries worldwide, many don't. Consider Europe, which enjoys a mix of heritages as wide and varied as the Americas for many reasons: immigration, refugees, or simply folk who wanted to live in a place with different weather, cultural, political or financial conditions.