Both of the CSA Johnston's were good commanders. They are not getting due credit because they were up against good Union generals. As a result, the disparities in men and material were telling. Against someone less tenaciuos than Grant, Shiloh would have been a tremendous CSA victory. You could make a valid comparison of Shiloh with Gettysburg--in both the CSA attack was repulsed. The difference was Grant not only hung on, he followed up. Lee's bacon was saved several times by a Union commander's failure to follow up: Gettysburg and Antietam were prime examples. He was fortunate not to be facing a commander like Grant, Sherman, or Sheridan on those occasions.

The Union was unfortunate in losing Nathaniel Lyon right at the start of the war at Wilson's creek. He was an aggressive, smart general, who secured Missouri from the very active insurgency, and he nearly destroyed the much larger confederate force before it could go on the offensive.

Language did play some role, but I think Didz has much overstated it. The biggest language issues I'm aware of came from the German's. There were several excellent German regiments who had drilled in preparation for war and Lyon relied on them. The loss of Lyon contributed to the rise of his subordinate Franz Sigel, who proved a very ineffective commander, and had muffed his flank attack at Wilson's Creek.

The Union had trouble with troop quality in the eastern armies, partly because they were more urban but also because they were often conscripted and NEW. The Union had suffered so many major defeats in the east that its volunteer units had largely been unable to gain experience and survive, and those that had were demoralized by a string of lackluster commanders and too frequent defeats. "Seeing the elephant" does you no good if you get squished under its feet. Their CSA counterparts survived, though depleted, to form a coherent veteran core.