Short answers, pulled from the story.
German cartographers Martin Waldseemüller and Matthias Ringmann published a world map in 1507 that placed the name America on the landmass now known as South America. They chose this name to honor Amerigo Vespucci, an Italian explorer who was the first European to suggest that the lands discovered by Columbus were not part of Asia but a new continent entirely.
The traditional theory states that hunters entered the Bering Land Bridge between eastern Siberia and present-day Alaska from 27,000 to 14,000 years ago. A growing viewpoint suggests that the first American inhabitants sailed from Beringia some 13,000 years ago.
The Thirteen Colonies in British America sent delegates to the Second Continental Congress in Philadelphia who unanimously adopted the Declaration of Independence on the 4th of July 1776. The document was written primarily by Thomas Jefferson and declared the colonies independent from the British monarchy governed by King George III.
The Panama Canal was completed in 1913 and connected the Atlantic and Pacific oceans. The United States carved out the Panama Canal Zone and claimed sovereignty over it after aiding Panamanians in a war that resulted in its separation from Colombia.
The United States is the most populous country in North America with 342.9 million persons. Mexico is the second-largest country with a population of 126 million and Canada is the third-most-populous country with 41.5 million.