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:

an era of negotiation.

is that an answer to your question?

necessary and proper clause. the congress shall have power to all laws which shall be necessary and proper for carrying into execution the foregoing powers, and all other powers vested by this constitution in the government of the united states, or in any department or officer thereof.