They never had a chance if the people of the Union stood by their guns and continued to support the war.
This was by no means inevitable. In a democratic society sometimes the People just get tired and give up. As we did in Vietnam.
Also, pig-iron didn’t fight the battles. Men did. And there were quite a number of battles where if things had turned out a little differently the South would have won its independence.
That wouldn’t have been the end of it, of course. There would have remained huge numbers of areas for conflict between the two new nations, and in all likelihood other wars would have ensued.
The general consensus among European soldiers was that the South would win. They based this on the sheer size of the area that needed to be conquered, the factor that had defeated George III in America and Napoleon in Russia.
But they didn’t adequately factor in the railroad, without which the North, despite its great superiority in materiel, could not have handled the logistics needed to crush the South.
And the extensive railroad net was a very recent development, really only in the decade prior to the War.
“Also, pig-iron didn’t fight the battles”
The point is that the north had many times greater industrial and agricultural output than the south. It also had twice the railroad mileage and a much better telegraph network.
A Union soldier had better clothing, food, tents, rubber blankets, transportation, utensils, and supplies.
The south was backward and underdeveloped. It could not even feed its soldiers.