By definition, it would in fact be the first time in history.
Quite. It's one thing for individual pilots to undertake suicidal actions in moments of desperation, something that happens at some point to every air force. It's quite another for a nation to undertake the deliberate policy of forming up whole units with the express purpose of suicide missions. If the US wants to create, essentially, kamikaze nuclear bomber wings, they have a hell of a uphill battle to follow. Who and how do they recruit for these formations? How do they indoctrinate them? How do they sell it to the rest of the military and the population at large?
In any case, we know what the tactics used by US nuclear bombers in the late-40s were going to be and suffice to say they were not at all massed wings of aircraft. Given the lack of weapons, intelligence, planes, crews, crew training, and infrastructure as well as the foibles of the first-generation nuclear weapons available at the time and the expected resistance from Soviet fighter aircraft, the odds of a late-40s nuclear attack on the Soviet Union delivering a knock out punch is rather low. This changes radically in the early-50s, of course, but by then the Russians have the bomb as well.