What factors caused problems and tensions between Native Americans and whites?

There were a
number of factors that caused
these problems.  Let us look at two of the most important ones

here.

First, a major factor was racism on the part of the white
settlers.
 (If the Indians were racist, it had much less of an impact since
they lacked the power to act
on any racism they may have felt.)  White
Americans tended to feel that the Indians were
inferior to them.  Therefore,
they treated them in ways that were sure to bring about
conflict.

Second, there was the simple fact that so many white settlers were

coming in to the various places where the Indians lived.  The fact that there were so
many
whites meant that they were constantly going to need to move out into
Indian lands.   As the
population grew and grew, conflict became more and
more likely.  

I should
note here that many people would
talk about different conceptions of land ownership between the
whites and the
Indians. They would say that Indians did not believe in owning the land where

whites did.  However, I would argue that this does not matter much.  Even in places
where (as
with the Cherokee and other tribes in the Southeast during Indian
Removal) Indians did believe
in land ownership and sedentary farming, there
was still conflict.  Whites still wanted the
Indian lands and were still
willing to push the Indians out to get it.