The ability of the CSA to do well in the early battles of the war gave them enough "street cred" to persuade the British to tilt their neutrality in ways that assisted the CSA. Had the CSA lost Bull Run, and other early battles I expect the British government, in spite of their other reasons to root for the CSA would have been less generous with financial openness, turning a blind eye to arms sales and so forth including granting the CSA belligerent status. The French will, as OTL, follow the British lead. This makes the CSA less viable, and of course it boosts Union morale while going against the CSA. The butterflies could be huge - if the CSA does not use this, and other early victories, to buy in to the concept that one Confederate soldier is worth five Yankees, they may address a more defensive as opposed to offensive strategy which might work better for them. It could avoid driving Kentucky out of neutrality as well as the offensive spirit that leads to many disasterous campaigns.