What role did nationalism play in America's western expansion?

Nationalism was justification for the U.S. to expand further driving all the Natives into small reserves.

Explanation:

Nationalism and Manifestation were the driving forces that led the Americans to move westward. They assumed that because God has given them the blessing to expand, they should.

basic principles: federalism, separation of powers, checks and balances, judicial review, representative democracy, limited government, rule of law, individual rights and responsibilities, consent of the governed, majority rule, popular sovereignty, equal protection.