How did american indian populations numbering in the millions fall under the dominance of much smaller groups of europeans

Describe the technology advancements that lead to explorers being able to sail great distances. [[ps: doesn't explain where. i am only speculating it's in europe.

What was gained through the gadsden purchase

When president johnson vetoed a law that would extend the freedmen’s bureau, congress reacted by supporting the veto and closing the freedmen’s bureau. writing a new law to show support for the black codes. overriding the veto and expanding the agency’s powers. drafting a law to prevent african americans from voting.