Fighting the Second World War with 1945 technology

How would the Second World War change if every side had technology from six years later?

The Allies gain the larger systemic advantage through shared research, production, advanced ASW, aviation, and potentially nuclear weapons.

Britain would enter 1939 with greatly improved anti-submarine systems and carrier fighters, while Germany would gain more advanced submarines and missiles. The Allies receive the larger systemic advantage because they pooled research and could apply it through broader industrial networks. Jet aircraft would appear over early-war battlefields, but production capacity would still limit how much advanced equipment each side could field. The largest discontinuity is the Anglo-American nuclear program: introducing 1945 knowledge early could make nuclear escalation part of the war's opening strategic calculations.