The invasion of Afghanistan was an attack launched by the United States and its allies, after the 9/11 attack. The main reasons why the United States invaded Afghanistan was that the U.S. recognized that the Al-Qaeda, the leader of a terrorist group had planned and caused the attacks of 9/11. Therefore, the principal objectives of this attack were to destroy Al-Qaeda and to refuse it a protected foundation of methods in Afghanistan. In this mission, the key ally of the U.S. was the United Kingdom.
The Louisiana Purchase gave the U.S. control of the Mississippi River and the port city of New Orleans, both of which were used by farmers to ship their crops and get paid
The effect that the issue of slavery had on politics in the 1850s was that it created divisions that ended the Whig Party and split the Democratic Party.