What is a big idea from 1491-1607 in US History?

One MAJOR idea from 1491-1607 is that we see the rise of European influence in the Americas. We have the English establishing colonies like Jamestown. We have the Spanish with their encomienda systems and their settlements. We have the Dutch and New Amsterdam. Perhaps most significant was how different the lives of Native Americans were becoming. The Columbian Exchange brought disease which decimated their population. The Indians also gained new technologies such as the gun and wheel, as well as horses. For the Europeans, they got maize and other crops from the Native Americans, significantly changing their diet and increasing their health.  

the us hoped to prevent any nations from leaning towards soviet union-based communism. the containment policy was established in hopes of keeping communism from spreading to new places.

(d) rivers.

explanation:

civilizations developed around rivers because their waters provided places to hunt and fish. also, as the rivers flooded, the lands around them became fertile. this allowed them to support farming. this is especially true of the nile river, which flooded the same time each year.