Which of these was the largest and most constant issue facing the United States during the era of "Manifest Destiny?"

Clearing out the Native Americans and Native people living there. Also actually getting out into the land was a struggle because it was really far away and you had to ride on horse back

Explanation:

the most famous of all the units fighting in cuba, the "rough riders" was the name given to the first u.s. volunteer cavalry under the leadership of theodore roosevelt. roosevelt resigned his position as assistant secretary of the navy in may 1898 to join the volunteer cavalry. the original plan for this unit called for filling it with men from the indian territory, new mexico, arizona, and oklahoma. however, once roosevelt joined the group, it quickly became the place for a mix of troops ranging from ivy league athletes to glee-club singers to texas rangers and indians.