It was an accepted idea or notion in the Washingtonian establishment during the Cold War that if one nation was allowed to fall under Communist rule, then neighboring nations would follow suit. This was a rationale for American engagement in Korea and Vietnam, and even in Central America in the 1980s. That idea perfectly fitted into the framework of the US containment doctrine.
It wasn't long before angry colonists joined him and insulted him and threatened violence. At some point, White fought back and struck a colonist with his bayonet.
Congress had to approve of military appointments. The War Powers Resolution was made so that the President of the United States could not commit to an armed conflict without the consent of the Congress.