Sicarius has a pretty good Independent Texas timeline. IIRC French support and internal politics (hilariously written, I might add) kept Texas out of the Union. When the civil war struck, Texas had gained recognition from France, and possibly Britain, and the US left them alone, even though they were running supplies into the south and getting rich off the smuggling operations. Didn't help the CSA much, but that wasn't the goal of the Texians in that TL.