Why do you thing the Brits backed the Confederacy so hard during the Civil War. It had a lot more to do than the Limeys wanting to ensure cotton supplies for their textile factories. The British were becoming increasingly worried about growing American power and wanted to see the country split in two to neutralize the threat as they saw it.
Of course, considering that PM Viscount Palmerston was a devious, finagling, Machiavellian SOB this shouldn’t surprise anyone.
That point of history ought not be lost on anyone. The notion of doing the job of our enemies for us while thinking that a mostly-conservative “half” of a non-united states would be stronger is an error.
After Antietam (9/1862) the Brits didn’t do too much heavy lifting on the CSA’s behalf.