Only half true, if that much.
50% (about $200 million) of 1860 US exports ($400 million) were Deep South cotton, that's all.
Almost everything else classified as "Southern products" could be and was produced outside the Deep Confederate South.
This was demonstrated conclusively in 1861 when Confederate exports were deleted from US totals, and excluding cotton, "Southern products" fell only $3 million.
So roughly $200 million of $400 million was Confederate cotton and, sure, that's a big deal.
But Northern "exports" to the South were also around $200 million, plus several times that number manufactured for Northern consumption.
That explains how Northerners earned money to pay for US imports and import tariffs.
So would loss of Confederate exports hurt the Union economy?
Of course, but even in 1861 the pain was not a much as secessionists claimed it would be, and in later years the Union adjusted, adapted & continued to grow economically without Confederate cotton.
You've been shown, again and again, and you simply ignore the facts provided by official US government sources, and keep trying to play your own tune.
"Value of Total U.S. Exports ..........$278,902,000"
"Total Southern Contribution ....................$252,000,000"
So would loss of Confederate exports hurt the Union economy?
And here you deliberately misstate the situation again. It is the loss of European trade that would hurt the Union. This loss did not occur *ONLY* because the Union put warships around Southern ports to stop the Southern trade with Europe.
Having no choice but to trade with the North, the Europeans did so, but without those warships, the Europeans would have chosen to trade instead with the South, and that would have absolutely wrecked the financials of various Northern businesses.
You keep running away from the point, because you can't think of a single manner to address the point honestly. When looked at honestly, the North was in a great deal of financial trouble, and badly needed a war to prevent it.