The South wanted freedom and independence from the North.
We have helped many other countries fight for such freedom and independence.
The South won the war of attrition, killing 300,000 Yankee soldiers.
It would be hypocritical to say the North fought to end slavery, since they still had slavery in the Northern/Union states during the war, and even after the war was over.
The South lost the war because of the North's brutal use of waging war upon civilians, i.e., Terrorism.
first of all, you seem to be mixing your centuries. It is true tha the US (WE) has helped many countries fight for freedom and independence, but that was in the 20th century, not the 19th.
Secondly, there were many reasons, on both sides, why the war was fought, but underlying every one of them was the issue of slavery. It literally was the bedrock reason for the sectionalism that comsumed the country from at least 1832, others say from the literal founding of the country. It was behind the secession movement and while Lincoln initially stated the war was to save the union, after the emancipation proclamation, it became a war to end slavery.
finally, war brings on brutality. It happens in every war and usually by both sides.
Now, I am a southerner, as I suspect you are, but regions do not determine facts. History is a record of what happened, not what we wish had happened.