It would be "d. how differently they viewed land" that was <span>often a source of conflict between Native American and Europeans, since the Europeans felt that in order to claim land, one had to use it in some way (as in farming or building homes). </span>
The answer to this question is “Congress”.
The answer is:
Multiple civil wars
Economic collapse due to inflation
Repeated invasions from all over....
Hope I helped!!!!^-^