If more cotton had been shipped to England and France, and held there, the Confederacy would have had an asset to convert to money.
But the English and French cotton merchants would have purchased the cotton and brokered it, at a profit, back to the US.
That would have made the English unconcerned about the Confederacy, and there would have been less dislocation in New England.
The US than makes tariff income on either imported raw cotton, or imported English textiles.
However, the Confederacy is still importing most of its war material.
And by May of 1862, it is using secondary ports. Its still not able to get much railroad equipment or rolled iron into any port and by March of 1863 the US is still blockading the inbound blockade runners.
The truth is that the US did not want to cut off the out flow of cotton, and some specie flowed into the Confederacy regardless of the blockade.
What the US could prevent was salt, coal, rolled iron, and pork from entering the Confederacy.
The credit terms and prices demanded by the blockade runners would have emptied the Confederacy of gold, it just might have taken longer.
And if the war had taken longer the US develops some other cotton policy, and perhaps permanently alters the source of its domestic cotton.