All southern ports combined didn't collect $7 million in revenue let alone $70 million.
I found this to.
Lincoln’s March 16, 1861 letters to the governors did not endorse or oppose the proposed thirteenth amendment.
The Corwin Amendment was ratified by:
Ohio — May 13, 1861 Rescinded ratification – March 31, 1864
Maryland — January 10, 1862 Rescinded ratification – April 7, 2014
Illinois — February 14, 1862 (questionable validity)
Once the Confederacy’s free-trade and low-tariff policy was announced around March 11, 1861 and the Corwin Amendment rejected by the SOUTH , all hell broke loose in the North.
On 18 March 1861, the Philadelphia Press demanded war: “Blockade Southern Ports”.
On 22-23 March 1861, New York Times “At once shut down every Southern port, destroy its commerce and bring utter ruin on the Confederate States”.
Leaders in the North decided they could not allow the South to go and taking about $70,000,000.00 tarif dollars with them wasn’t going to happen.
All ships would come South for free trade and LOW TARIFFS and of course bankrupt the North.
April 12, the war was on.
In actual fact the North lost all southern trade and taxes for the next four years, plus added in something around $3B in war direct costs, eventual total cost around $7B and came out of the war stronger than when it went in.
But by all means think that the North spent this immense sum based on a financial calculation that it couldn't afford to lose $70M in southern tariffs (itself a gross exaggeration, real number is probably somewhere around 1/3 of this amount).
IOW, the Union spent $7,000 million to "protect" <$30 million/year in tax revenue.
If the Confederacy was an independent country then how would their tariffs have affected the U.S.?
Leaders in the North decided they could not allow the South to go and taking about $70,000,000.00 tarif dollars with them wasn’t going to happen.
Where did you get that figure from?
All southern ports combined didn't collect $7 million in revenue let alone $70 million.