Oh man, one of my favorite topics. Are we including the first and second silesian wars in this?
A faster advance in the first silesian war, and a bit more confident action would have netted Prussia all of Silsiea, instead of letting Austria keeping their rump Austrian Silesia.
That would have formed a good jumping off point for the Seven years war, as well as a better defensive line.
If we are sticking to the Seven Years War itself, a solid victory at the Battle of Prague would do wonders for changing the early course of the war.
If Winterfeldt's assault upon the Austrian right flank on Sterboholy had carried the day in their first attack, or if either he had been there a bit sooner or the Austrian counter attack a bit later in developing, the whole battle would have developed differently. It would have been the Austrian infantry thrown back in confusion, right as the Prussian horse was engaging and driving the Austrian horse from the field. With both the horse and foot on the right flank victorious, the Prussian horse would not have had to fall back due to taking flanking fire from Sterbholy.
The Prussian horse would have had a free shot at the artillery that had been playing havoc on the Prussian advance all morning.
With the right flank broken earlier and at less cost, the Prussians would have had the time and men to roll up the entire Austrian line, and the cavalry to seal the deal and run down the stragglers. Had this happened, much of the army would have been defeated in the field, instead of allowed to fall back into Prague itself.
If Prince Moritz had showed up on time leading the right column of Keith's corps, with a few extra pontoon boats to cross the Moldau and block the retreating Austrian right wing, they would have netted nearly 16,000 prisoners, who would not have been able to link up with Daun's force.
That alone would have deprived Daun of nearly 16,000 troops. Which would have put him nearly at parity with Bevern's corp, assigned to observe him as he fell back from Prague. Maybe Bevern chances an engagement? If so, it would have been a very good opportunity for him. Crushing Daun before he can rally and mass his force means no Battle of Kolin.
With only 20,000 troops to start with, Daun would have taken the field a month later with only 44,000, and not the nearly 60,000 he was able to mass when he moved to relieve Prague. By the time he arrives at Prague, he probably has only around 40,000. That has big implications for the Battle of Kolin, if it is even fought.
This is all assuming Prague is even standing at the time and there is something to relieve.
With Prague captured and the Austrians crushed once or twice in a little more than month, Frederick is free to seek money and provisions from all of Bohemia while massing his forces against his other foes. The Austrians would have not been able to take the field again in 1757. This would have given Frederick the time and space he needed against the other powers.
I'm sure the war would have dragged on, but it would have gone significantly better with Frederick playing wack-a-mole with a bigger hammer. I'm sure the Austrians would have taken the field in 1758, but fighting the war in Bohemia means they aren't fighting in Silesia or Saxony, protecting Prussia's sources of supply and manpower.
If Prussia wins big enough to force Austria out of the war, even for a just a year or so, then all bets are off.