It goes to show that History is seldomly a linear experience but something which can cause unexpected consequences.
Very true.
Only two countries have ever invaded the mainland US - Britain and Mexico.
Actually, only Britain has officially invaded the USA. As for Mexico, during the 1910-1921 Mexican revolution, on March 9, 1916, a warlord of the Mexican State of Chihuahua known as Pancho Villa, aka Francisco Villa, crossed the border into the USA and raided the small town of Columbus, New Mexico with his force of 500 men and killed 17 Americans. Mind you, the locals were well armed and killed a bunch but then the United States Army 13th Cavalry responded and drove Pancho Villa back into Mexico. The Mexican government in Mexico City didn't know about the incident until the US Ambassador told them the USA was going after Pancho Villa and President Woodrow Wilson ordered General Pershing to chase and kill Villa and one of his staff officers was a young Lieutenant called George S. Patton. The next year, the USA entered World War 1 and Pershing was the Supreme Commander of the AEF (American Expeditionary Force) and he became America's first Five Star General. Patton then became a brevet Colonel in World War 1 and later on he became a Four Star General in World War 2 known for his super aggressive tactics and successes in the war.