Everything Bad Brain and Dutchoper72 have said about WWII and America's involvement following the Japanese attack on Pearl Harbor.
Cannnnn you feeeeel the ignorraaaaaance tooooniiiiiight?....it is wheeerrrreee we arrreeeee....
"British would have lost the war if the 'Japs' hadn't attacked the US"...
False.
The German Luftwaffe did have a considerable run of terrorizing Allied ships and overpowering air superiority, but that is mainly due to an increased size and militarily-trained force upon the start of the war. However, these were decreasing
well before the US entered the war, as British production soon passed that of the Germans. Before Pearl Harbor, the UK was already cranking out more ships AND aircraft than the Germans. German attacks were reduced, and--as Bad Brain correctly stated--British bombers were already striking mainland Europe before our involvement. The British had control over the Middle East and, therefore, nearly outproduced the entire Axis forces in total oil production--something Germany was beginning to have issues with. They were inching towards the oil fields from North Africa, but the British did a good enough job in
overall defense and counterattack of the region that the eventual US landings were essentially superfluous.
British had produced jet craft, though not to the specs of the German productions. Also, British bombers were increasing in amazing strides. This, combined with new, brilliant, tactics in shared/split responsibility of bombers (which were eventually adopted by the Americans in our bombing runs) lead to greatly reduce the impact of the EVENTUAL (remember they were still late in the war) terror the German jets INITIALLY caused.
Simply put, before we got involved, things were becoming more stable for the United Kingdom against the Germans.
That doesn't even factor the USSR into the equation. The Germans screwed up royally in Russia, even though they quite nearly did break Moscow AND Leningrand AND Stalingrad. However...Russia is more than just those three (large) cities. Russians had (sorry to sound cruel about it) more bodies to throw at the Germans than they could know how to deal with. They were cranking out tanks and weapons beyond what the Germans thought was possible. Their oil and steel production downright put the entire combined Axis forces to shame. The great German Luftwaffe was getting thrashed in Russia. They moved through Eastern Europe
so swiftly that...really any Allied invasion on Western Europe is
more than likely something that wouldn't even have been necessary to defeat the Germans.
Seriously.
Also, none of this even factors in the seemingly-inevitable self-collapse of their forces due to unstable-at-best leadership.
Oh yeah--one more thing...Germans did not ever produce atomic bombs. Dunno where you heard this but it's...well...just plain false. True, they were producing like crazy, but let's not forget that all of those Manhattan Project guys that defected, took all of that genius with them, trashed some stuff in their wake, and that the Germans just plain never got anywhere near the production part that US had.