How did Franklin Roosevelts speech declaring war after Pearl Harbor change history?

hope this helps

in basic terms, because of Americas involvement in WWII, Germany and japan didn't wipe out England or russia. with those two countrys gone gremany would have owned Europe and all it's resources making them the supreme power. they already had the most advanced technology of that day, and the will to use it at any cost. without our involvement all of Europe would have fell and eventually we would have fell and the rest of the world would have followed. in my personal opinion Hitler would have taken japan out last thus turning Germany into the rulers of the world. FDR's speech rallied the world. it gave every free country hope and a hand through one of mankinds toughest moments. it helped boost Americas production and economy 100 fold leading us to the superpower status most take for grantit today and was the last nail in hitlers coffin. at least that's my opinion. Tommy marshall.