Well, I think like you that G A Custer gives the last checkmate to this war.
Appomattox station was the ultimate battlefield for this war 8 April 1865.
They took the train full of Confederation supplies, artillery based on North and captured also G L Walker.
G R Lee knew that war was definitely finished for them.
Three names are important for this war, a mix of bravoure, honor, and their tenacity: G. T J Jackson CSA , C J Chamberlain US, G. G Custer US.
I can make errors, I m not American, my visión of things comes from Europe.
Regards
As you have noted Custer played an important part in the War but sometimes he got carried away with himself and his station in life. I have a quote below from James Longstreet's
From Manassas to Appomattox which shows Custer being brought up by his betters.
"General Custer rode to Captain Sims to know his authority, and, upon finding that he was of my staff, asked to be conducted to my head-quarters, and down they came in fast gallop, General Custer's flaxen locks flowing over his shoulders, and in brusk, excited manner, he said,-
"In the name of General Sheridan I demand the unconditional surrender of this army."
He was reminded that I was not the commander of the army, that he was within the lines of the enemy without authority, addressing a superior officer, and in disrespect to General Grant as well as myself; that if I was the commander of the army I would not receive the message of General Sheridan.
He then became more moderate, saying it would be a pity to have more blood upon that field. Then I suggested that the truce be respected, and said,--
"As you are now more reasonable, I will say that General Lee has gone to meet General Grant, and it is for them to determine the future of the armies.""*
Regards
David
*
http://www.civilwarhome.com/longstreetappomattox.html