The leading theory about how early humans arrived on the American continents is that they traveled from Asia to North America via a land bridge known as Beringia, which connected Siberia (in present-day Russia) to Alaska during the last Ice Age. This land bridge existed because sea levels were much lower due to the large amounts of water trapped in ice sheets at the time.
From there, these early humans gradually made their way down into the Americas, primarily through inland routes and possibly along the West Coast. This migration likely occurred over thousands of years, with groups spreading southward into what is now the United States and further into Central and South America.
So, while your statement about traveling from "America to South America" is incorrect, it does capture the idea that there was a land connection that facilitated human migration into the continent. Early humans did not traverse from America to South America as united landmasses but rather migrated down from the north after arriving in North America.