On average, the Americas move about one inch further away from Europe and Africa per year. The landmasses move away from each other due to a phenomenon called continental drift, where the tectonic plates that continents sit on are in constant motion and can drift toward and away from one another.
The idea of continental drift was first developed by a German scientist named Alfred Wegener in 1912. He noticed that the western coasts of the continents of North and South America looked like they could fit into the eastern coasts of Europe and Africa. He proposed that the two landmasses may have been one massive landmass at one time. Archeological findings in South America and Africa supported Wegener's argument, because similar rocks and fossils can be found in both continents near where the "supercontinent" eventually split.
Today, continental drift and plate tectonics explain many parts of the Earth's surface, and scientists have even been able to measure the continents drifting apart year after year. On average, the landmasses of North and South America, and Europe and Africa move about 1 inch further apart each year. In millions of years, the landmass of North and South America could collide with Australia and Asia.