Well they weren't too pleased haha.
Some indian tribes were friendly and some attacked the new settlers. Over time the indians saw settlers colonizing as a threat to their people and were more often violent. But in the beginning they would trade with the settlers.
Many of the native americans were un-able to adapt to the changes in their homelands. With the bison hunted into endangerment, and their farmlands confiscated, many were unable to survive. The indians were also taken as slaves, so this created fear as well. So their reaction was to fight the settlers for their homeland back, which caused allot of death.