The correct answer is distrust of the federal government among American Indians.
The federal government and several groups of American Indians had negative relationships throughout the 19th and 20th century. The federal government has forced different groups to leave their native lands (like the Cherokee during the Indian Removal Act). Along with this, there were several military encounters between the two (like Custer's Last Stand).
The federal government and their constant encroachment on Native American land and the promises broken by the government continue to haunt the relationship between these two groups.