In 1940, the USA only have 48 states yet
The United States of America are in 1940 the country with the third-biggest population worldwide (about 140 millions), and an industrial potential several times bigger than the next-strongest states put together. While looking much weaker at the same time, almost deceptively so.
Politically, President Franklin D. Roosevelt pushed his "New Deal" through and is popular among the Majority of the population (especially the big city folks, Minorities, and white Southerners), even if his results were mixed - the economy recovered, but unemployment's still about 15%, and in 1937 there was the small Recession. Also, there's a big isolationist Minority who isn't content with Roosevelt supporting Great Britain with lots of money and arms against Nazi Germany. His Democrats still have an overwhelming majority in Congress, even after the Republicans almost doubled their mandates during the elections of 1938 - but in Practice, the Republicans allied with the Southern Democrats, forming the Conservative Coalition, to prevent even more "New Deal" measurements.
During the World War[]
Hence, the Situation is difficult for Roosevelt. He would love to mobilise (in 1940, the Army's just about half a Million Men strong, more comparable to a country like France), let alone declare war on the Axis Powers, but he also has to consider the elections in November. His second term will run out, and so far no US President has ever gained a third one. But who should then become his successor in these difficult times? Vice president "Cactus Jack" John Nance Garner? Secretary of State Cordell Hull? Secretary of the Treasury Henry Morgenthau, Jr.? Or even the eccentric Secretary of Agriculture Henry A. Wallace, or Secretary of Labor Frances Perkins? And who will run for the Republicans? Thomas E. Dewey from New York, who brought Al Capone behind bars? Earl Warren, who's even popular with Democrats in California? Highly estimated Senator Robert A. Taft? Former Secretary of War/State Henry L. Stimson? An outsider like Henry Ford or Charles Lindbergh? Or even the "defector" from the Democrats Wendell Willkie, or ex-POTUS Herbert Hoover? - At the end, even when FDR didn't announce his candidacy, his supporters simply wrote him in, and in late May his party has him as good as nominated. The situation among the Republicans was less clear, until they decided for Willkie during their convention in June.
Even selling arms to the Allies is difficult because of the Neutrality Acts which forbade this - until FDR found a way that allows them to buy arms as long as they pay in cash and transport them on their own ships ("cash and carry"). Other than that, he only managed to implement the Neutrality Patrol since September 12th of 1939, which has the US Navy guard a zone of 300 miles east of North and South America. And on January 25th of 1940, he authorized the Atlantic Weather Observation Service, which might come useful in a war.
