In the late 1920s the US War Department devised a plan to destroy the British Empire. American troops would invade Canada and the Caribbean to draw out the British Navy, which they then intended to destroy leaving the Empire undefended. The USA would assume influence in these areas and gain economically.
WW1 had caused insularity within the US and there was increasing anti-British feeling. The United States was also caught up in its own Imperial adventure. The plan was abandoned on the basis that regime change in the UK would be accomplished by Hitler. The American Embassy in London took notes on Britain for the above purpose until WW2. This process was reinitiated after the war, but not through war.
The Secret US Plan to Overthrow the Brotish Empire by Graham M Simons