Grant was within a few thousand casualties in three months that it took Lee three years to accumulate. Had the war continued another year, I believe the North would be fighting another insurrection within itself as a result of the bloodbath Grant was bringing them.
The North endured the casualties, those casualties brought victory. Fort Donalson falls, a Confederate army surrenders, and Tennessee is open all the way to Muscle Shoals Alabama. Vicksburg falls, a second Confederate Army surrenders, the Mississippi is in Union hands and the Confederacy is split in tow. Chattanooga relieved. Braggs Army driven off. After the Overland Campaign, Lee’s Army penned in Petersburg where it will wither away to a shadow of its former self. Within the year, a third Confederate Army would surrender to U.S. Grant and the Capitol of the Confederacy is in Union hands. The Confederate government on the run, desperately trying to avoid capture. Casualties are the price of victory in war. Grant brought the Union victory in war.