first off, first post, i'm a teenager without much research experience but i'll do my best, so don't bite my head off
now, for Ramifications of Just Bismarck wreaking that fleet, we could see Hitler focus Much more on the Navy because of the fact Bismarck has just proven it's superior. what this might mean is, no immediate consequence, but a change on how the Navy runs the war and their support. Graf Zepplein might be finished as well, so even more to worry about for the british
as for the NYs vs. B/T, i liked the assessment off the battle, and I'll need to look at it, i think you might be Forgetting Bismarks Secondary armament. 12 15cm guns aren't just doing nothing, and even with the advanced america torpedoes LATE in the war, destroyers had to get to a close range to fire. the 5in/38cal guns on the Fletchers, Allen M. Summers, and capital ships had a range of 10 miles. the 38 cal from late war, they Out-ranged the late war US torpedoes. the 6 in guns and even the 105mm guns will be firing on the destroyers LONG before the get to firing range. also, with Torpedo wandering, them hitting their target is unlikely, plus warhead detonation as before. add to the fact that the only way to take these monsters out of action is Hundreds of Heavy shells or equivalent and a wreaked steering system and the allies have a hard time. not sure the difference in explosive power from Swordfish torpedoes and MK8s, but something to note. also, PE and AH have torpedoes of their own.
maybe all addressed and I'm oblivious, but still putting that out there. Germany's ships(at least of Admiral Hipper/Bismark classes) are very tough ships, so we may see even with american superiority in numbers inferiority in battle. also depends on the commanders of the 2 groups.
as for the Reprecussions of the event, Roosevelt now has his casus belli and can now go to war. the Atlantic fleet carriers are now in the fight and some more assets could also be moved from Pearl to the East and the Eighth Airforce is sent over earlier. which means if the American Flattops and modern battleships are constantly hunting and containing the German surface fleet, Japan gets an easier starting time in the Pacific when war breaks out. while fighting might be fiercer, all assets are for Europe and Capitals ships, especially Carriers, won't be done for quite a While.
as stated, in the end, the Axis still lose, but is messier and harder. and that's without even touching the soviets