The President of the US for all but the last 5 months of the war was Franklin D. Roosevelt. He died and was succeeded by his Vice President Harry Truman, who made the decision to drop atomic bombs on Japan.
The military leaders included chief of staff General George Marshall, General Dwight D. Eisenhower (European commander-in-chief) and General Douglas MacArthur (Supreme Allied Commander in the Pacific).
Clarification - America was not the only allied power involved in WW2, and did not 'win' the war.
It seems that the popular notion in the USA is that they were the only country involvd and 'won' the war single handed. The USA and British, Russina, Australian & New Zealand and a host of other European countries served to defeat the Axis powers. The Allies were led by a coalition of military leaders representing these countries.
Blame 'Hollywood' for the continued mis-understandings associated with this question.
MM
It seems obvious that the previous answerer would have us believe that the US was led by SOME OTHER COUNTRY to victory in World War 2, but I believe the question-poser just wants to know the name of the US President at the time.
Because FDR died in office before the war was ended, Harry "Give 'em hell" Truman was in office and made the decision to "Drop the Big One now" on Japan. Twice.
FDR franklin D Roosevelt
America declaring war on Nazi Germany and joining the Second World War in Europe.
lake erie
She led the french to victory during the Hundred Years' War
What led factors led to President Nixon's victory?
Pearl harbor. Hitler killing jews. Invasion of poland. America is allies with france. America had to help allies.
Woodrow Wilson
FDR.
Industrial output...which ultimately led to the A-Bomb.
looting
The two military options that led to the end of World War 2 were the victory in Berlin and the use of atomic bombs in Japan.
America joined world war II when peril harbor was bombed by the japanezze
America declaring war on Nazi Germany and joining the Second World War in Europe.
Post-War labor disputes
George Washington
America contributed to World War 1 before 1917 by supplying the warring countries with military goods. This led to an economic boom that sustained America's war spending when it eventually entered the war.
the spread of the idea of liberty at home and abroad.
The attack on Pearl harbour