No, it was the firearms that did that.
How ironic that after injuring, bloodying, defeating, and dragging the "South" back into the Union, that they then referred to these as "United" States.
I know that secession hurt feelings, and even angered, but "injured" is too much of a distortion. The "South" was not "an enemy force that was determined to rip apart our nation".
I am a Yankee and must admit that the study of the Civil War and the results are not the historic topics in northern schools as much as they are in the south schools.
Please, I'm only making an general observation based on personal experience and not a statment of absolutes.
When I moved to NC a decade ago, I was a substitute teacher for 8th grade NC history. I had to study up and let me tell you, I was quite interested in the "other side of the story"!
I know for many of those in the south, the war will never really be over, largely in part because the south had the better army and the better generals. By all reason, the south should have won. Then came Sherman... after which came all the broken promises...
I must admit that I have a whole new understanding for the southerner's position in this matter. I'm not going to argue the morality of the war or the outcome. It was a tragic event for our country and for the men and boys who took part.
As for the flag, I see nothing wrong with flying it, or wearing it, or anything else. It's a part of history and represents a very troubling time and something very significant to those of you in the south.