Answer:
The major downfall of the Articles of Confederation was simply weakness. The federal government, under the Articles, was too weak to enforce their laws and therefore had no power. The Continental Congress had borrowed money to fight the Revolutionary War and could not repay their debts.
Timeline of Westward Expansion.
Manifest Destiny. ...
Louisiana Purchase. ...
The Corps of Discovery Expedition (Lewis and Clark Expedition) ...
The War of 1812. ...
Missouri Compromise and the Kansas-Nebraska Act. ...
Monroe Doctrine. ...
Indian Removal Act and the Trail of Tears.
Neutron bomb and hydrogen bomb