Learn your history, buddy. The United States was ill prepared for war because of the isolationist mentality of the government at the time. However, in '38, FDR advocated to his military advisers that he wanted 10,000 military aircraft ready by `40. In `40 he sent 50 overage destroyers to Britain. Also in `40, the Selective Service Act was passed and the US began drafting and training troops. Then, in early `41, FDR got Congress to pass the "Lend-Lease Act" which sent arms to Russia and Britain with no repayment needed. It wasn`t until December of `41 that Japan attacked and then Germany declared war on the US. The attack on Pearl Harbor just pissed off the country and made it possible for FDR to do what he wanted to do from the start. Had those things not happened, Europe would have fallen to Hitler.
Quite frankly, if this happened today, people would say it was a conspiracy created by FDR to get involved in the war (September 11th anyone?