Joe the North fought with one arm behind its back. The South was never a threat to the North. It is all in your mind. There was military action along a huge front from MD thru Kansas. But the South was never going to invade and hold the North. Ever.
So you keep saying but the fact is that Lincoln went through a long list of Union generals before he found the few who could turn the Union's natural advantages into battlefield victories.
A lesser man than Lincoln (Democrat President Buchanan comes to mind) could well have frittered away Union assets allowing Confederates to achieve their wildest dreams, and more, the virtual destruction of the United States.
So your claim that the Confederacy was "no real threat" rests 100% on the relative success achieved by Union commanders at such places as Antietam, Gettysburg, Vicksburg, Nashville & Petersburg.
Lesser Union leaders would have made the Confederate threat very real indeed.