As other answers have said, life changed dramatically and became much for the worse for Native Americans after the arrival of the Europeans. First, the Native American population was rapidly reduced by the introduction of European diseases for which the people had no immunity, such as smallpox, cholera, bubonic plague,...
and whooping cough. Some estimates run as high as a ninety percent mortality rate among some tribes—a devastating figure.
These very high death rates had a disruptive effect on Native American societies, and this was followed by having to contend with increasing numbers of foreigners who possessed a superior weapons technology and yet little to no understanding of native cultures. Native Americans had to adapt to survive, and they did so in a number of ways, which included merging tribes, attacking settlers, allying with one group of settlers against another, entering into treaties with Europeans, and adopting Western technologies when feasible. Other survival attempts, once the United States was established, including petitioning Congress or the White House for redress of grievances and trying to persuade people in power that their native cultures were behaving according to white expectations.
Another devastating effect on Native Americans were forced relocations from their ancestral lands. Not only did many people die due to the rigors of the journeys, but cultural trauma followed, especially as most Native American religions were tied to a particular piece of land whose gods were understood to offer protection to that group only so long as they remained there.
Culture clash did not go well for the Native Americans, who were badly outnumbered by hostile invaders with lethal technologies and a vastly different idea of social organization.