Imagine for a moment that Lee won Gettysburg? Where would his Army have gone next? Certainly they would have moved on to Harrisburg and camped there, replenished supplies and cut the rail line between Philly and Pittsburgh. But then where? Philly? Back to Baltimore and DC? I think just capturing Philly would have won the war for the South because NYC, New England and all the western states would have been cut off from DC. Fun to speculate 150 years later.
That it is interesting — I have never thought more beyond “Lee counts on victory in Northern Invasion to break will of the Union” narrative.
You are correct, a victory followed up action could have cut the Union “in half”