Was the outcome of the Civil War the beginning of the end for the American civilization?

As a result the individual states lost much of their sovereignty. If that sovereignty had been maintained, it might have been tough to muster support for the US involvement in WWI. Thus, the Europeans would have to have come to different terms to end the war. Thus WWII would not have happened. Thus, the West’s strategic need for oil, and involvement in the Middle East would have been diminished, and Palestine would never have become a casualty of East/West geopolitics, thus there would have been no modern Isreal or any need for one since there would not have been a holocaust in the first place.
No Cold War, no Vietnam.
And none of that might have happened if the South had been permitted to withdraw from the Union. No doubt, there would have been a strategic accomodation with them, just like we have with Canada today, so nothing lost there.

But now, it is the US’s continual involvement in these disputes that diverts our resources. And it is the heated debate about the power of Central Government that divides the nation.
And none of that might have happened if the South had been permitted to withdraw from the Union.