Well... I see no statements to select so..? However factors that contributed to the decline in quality of life of Native Americans in the 19th century were:
*Disease; They still battled disease brought by Europeans that pretty much destroyed most tribes, because they had no medicine to treat the diseases and had never encountered anything like them.
*Racism; Colonists and others believed that Native Americans were lower then themselves because they lived differently then they did. They traded as currency instead of using paper money or coins. They spoke a foreign language and had many traditions the Colonists felt were unnecessary or "weird." They were not educated by "white people" standards. They ate what the land gifted them. They lived in houses made of animal hides or mud. Some lived polygamy marriage lifestyles (many wives.)
*Land; Colonists were greedy and wanted land. They believed that since the Native Americans were not "as good" as themselves and were "savages" that the land was theirs for the taking. The Native Americans of course were forced from their lands and onto reservations which was of course very unfair and a d¡ck move for Americans.
Pretty much sums it up.