How old is America?

The answer to this question depends on how we define America. America can refer to the continents of North and South America, but it is often used solely for the United States of America.
Geologically speaking, North America formed between 1.5 and 1 billion years ago out of the Laurentian craton. South America formed when it broke off of the larger landmass Gondwana about 35 million years ago. The two continents merged about 20 million years ago to form a continuous landmass.
Perhaps America is as old as the human settlement on the continents. There is some debate as to exactly when this took place. It is certain that people arrived in North America by the end of the Ice Age at least 10,000 years ago. There is evidence that the first Americans arrived even earlier though, possibly 17,000 years ago.
The name of America is attributed to the Italian-born geographer Amerigo Vespucci. After returning from his voyages to South America in 1502 a map was published in 1507 naming the newly discovered continents "America".
The nation of the United States of America was created when it declared independence from England on July 4, 1776. The United States is often referred to simply as America by many people and therefore, this date is often can be considered the beginning of America.
http://www.bbc.com/earth/story/20170328-the-first-people-who-populated-the-americas

This is an interesting question, and there are several possible answers. Colonialist European histories traditionally teach that America was "discovered" by Columbus in 1492. This suggests, however, that it had not existed before that, when in fact North America had been an inhabited continent since the Ice Age, when Native Americans first arrived from Asia. However, we could argue that the continent as it existed at this time was not "America." The name "America" was given to both American continents by a Spanish cartographer in the early sixteenth century. It was named for the explorer Amerigo Vespucci.
The United States of America, of course, did not come into existence until 1776, but before this, colonies were well established in the country. The first British settlers arrived in the United States in 1585. Again, the question is: What do you mean by "America," and what makes America what it is?