On second thought let me qualify a bit:
I suppose it's conceivable that there could have been an authoritarian, militaristic regime in Germany that had the ambition to expand and therefore alienated the Western powers, and yet also had the capability to eventually develop an A-bomb first. It would be difficult; they'd have to both avoid alienating and thus decimating their own intellectual community (which included people like Lise Meitner, who was from Austria and deemed "Jewish" by Nazi categories--indeed unlike many Germans and others the Nazis called Jewish, she would agree she was that--and lots of other non-Germans drawn into Germany by Germany's long-established leadership in science and technology). And also gain access to the global resources and also a big, long-running expensive program, one that would not alarm foreign competitors, not only Westerners in France, Britain, and the USA but also the Soviets, into launching crash programs of their own, one they could hide from foreign observation. To do this, they'd have to make it a national priority, and yet avoid tipping anyone else off, and have to carry out the intensive work of separating out suitable fissionable isotopes while safe from bombing interdiction. Therefore they'd have to do it either during peacetime, when foreigners had no excuse to be flying over German territory spying out their doings and they had access to global markets (again without tipping off their rivals), or else after they'd conquered a very broad territory and held it securely with air superiority over deep terrain. In the latter scenario they'd have to either secure peace after conquest--which seems unlikely unless one supposes the British would go for a truce, and so would the Russians--or they'd have to divert really large fractions of their limited national resources to a project with some question marks over its eventual success and utility even if they should technically succeed, while meanwhile fighting a conventional all-out war for their lives. Before the Manhattan Project was done, it was not after all certain that even if a bomb of sorts could be made that it would be of a size that it could be delivered! So prior to someone else demonstrating that the thing was practical as a weapon, investment in such a venture would be a gamble.
Given the USA's economic and geographical situation, it was a gamble the Americans could figure they could afford to make and lose, even in the middle of a total war. For Germany alone to roll those dice, the cost of losing would be much starker, and the odds of winning were clearly lower.
Anyway, politically speaking such a situation, where Germany had both the intellectual and material/geopolitical capital to risk in it, would be a long shot. And it definitely would not be Nazi Germany, however otherwise grim it might have been. The Nazis, if they were going to win, were going to win without nukes. That's what the regime calculated; it covered the bet with a certain level of effort, but even given an ASB gift of the most dedicated and capable cadre of first-class scientists to help them along I don't believe the Third Reich could possibly have done it, certainly not bearing in mind that no one knew going in just how much effort of what kinds it was going to take.
If a time-travelling ASB had disclosed to them the minimal requirements and the most direct path to a working bomb, allowing them to avoid wasting time in dead ends and promising approaches that turned out not to be the most cost-effective way to go, that would be a help to be sure, as would be the assurance that the effort would pay off eventually. But that's a different, ASB, scenario; the only way to get there realistically is to allow some other power to beat them to the punch and then pinch their results via espionage--and somehow hold the more advanced power at bay while they catch up. Even then, it would be hard to do it given Germany's limits, and the foreigners would know how to recognize efforts that were on the right track and take steps to stop them. Including if necessary a pre-emptive war on Germany involving use of nukes.
Anyway if in any long-shot scenario Germany could come up with practical A-bombs first, I am very confident that even in the best possible case for Germany, it would have been later than 1945. Germany would just have to spread the effort out over more years and no one could really get started much earlier than the British and then Americans did OTL. Building up a stockpile such that they were a major war-winning weapon system instead of a mere psychological demonstration would have taken more years, again it took the Americans, riding high on global victory with an undamaged and indeed revived homeland and effective supremacy over most of the globe, to build up a decent stockpile; Germans would take at least as long and probably longer.
So we can't be looking at an "A-bomb armed Germany" scenario much earlier than 1950, with one thing and another, and by then it seems likely someone else, even belatedly, would manage to catch up. 1950 is only reasonable if Germany avoids the decimation of a major conventional war in Europe, thus Britain will also avoid that battering, and hence be more capable, even if the Americans slumber away cluelessly. And the Soviets, while lacking the world-leading sheer economic capability of the USA, had everything else needed--their own world-class scientists and technicians, abundant (if hard-won) resources, deep swathes of land far from prying foreign eyes, and the ability to ruthlessly mobilize what resources the regime could scrape up to the orders of the top boss. Between Britain and the Russians I think even if the Germans (non-Nazi ones) manage somehow to get there first with A-bombs, by the time they have enough of them to matter, one or the other or both of these rival powers could match them.