In Europe and in Asia there where only two country left with democracy Around june 1940 France falls under Germany then only country left as a democracy in Europe is British so US president Roosevelt made a decision in March 1941 "Lend-Lease Act"which permitted the lending, leasing, selling of arms ,ammunition and food to any country whose defence the President deems vital to the defence of the US interest and security of the region but USA w't directly involved in war because US Senate is opposing in any direct involvement due huge lose in first world war, however Winston Churchill was desperate that USA must enter in to war ,he was also convincing Roosevelt about his position. Eventually on December 1941 the Japanis imperial navy bombed US Pacific fleet in Pearl harbor ( Hawaii island) that made Roosevelt to convince US Senate and his people to enter in to war .in November 1942 code name Operation Torch is first foot step in to the war in North Africa by USA against Germany.