And technically the only reason he needed to enter the war was that his allies were attacked. Yet he didn't? Hmm something's not here... The fact is for the littlest act of agression we could have declared war. Hell before Pearl Harbor, the U.S intercepted a message meant for Mexico offering it parts of the U.S land if it helped in the war effort. Luckily it was intercepted because who knows what damage it could have caused.