Despite the story that Grant was given overall command, he was not permitted to recall Banks' Red River expedition.
Franz Sigel and David Hunter were allowed to continue to compile defeats in the Shenandoah Valley and Ben Butler did nothing more than take up space at Bermuda Hundred.
What happened by the time the war ended. The troops in Louisiana were transferred elsewhere. Canby relieved Banks.
Phil Sheridan was given the field command in the Shenandoah Valley and Grant gave him direct instructions, not filtered through the War Department, and General Terry was given command of the army portion of the 2nd attempt at Fort Fisher, with explicit instructions to "cooperate" with navy commander David Porter, at the expense of Ben Butler.
So despite the story, it looks like Grant and Meade were working under some material constraints, and the Overland Campaign as fought, was an attempt to proceed within those constraints. The casualties that occurred were caused by the fact that General Lee forced the fight in the Wilderness, and Grant and Meade wanted to fight the key fight before Lee had the advantage of the Richmond/Petersburg fortifications.
The casualties were high during the Overland campaign.
However the election was settled, Sheridan burned out the valley, Sherman captured Savannah, Terry and Porter closed Wilmington, NC as a blockade port, and Charleston was cut off.
After the 1864 election, neither time nor placating political personalities were factors, and the United States closed out the war much faster than anticipated.
The Confederacy did not get another Spring and Summer, they got a Winter and a couple of extra weeks.