1) Why would the South invest in the extensive internal improvements the north did that made automobiles viable?
2) Again, few nations relient on a major crop for export managed to industrialize successfuly, even after the crop's value declined.
Why does the CSA?
Actually, I do believe that the Confederates, in order to meet the demands of the on-going war effort during the OTL Civil War, did industrialize to a rather significant extent (although still nowhere near the development of the North). And, perhaps if a well-liked predacessor of Jefferson Davis with the goal of mass-industrialization in mind was to gain power, you could see a moderately industrial economy emerging in the South by the beginning of the 20th Century.
Second, the Agrarian South really had no common interests with the West (Beyond East Texas), the economy of the West had a different basis, and the Western Economy was more closely linked with Northern industrialization than the Southern agrarian / cotton / slave based Economy.
I'd have to agree. In reality, it seems more likely that the CSA would expand south into the Caribbean. Decaying colonies and insignificant states such as Cuba, the Dominician Republic, Central American Republics could easily become prey to Southern ambitions. Of course, the question would be how would the South come to satisfy such ambitions.
If the CSA comes into existence in 1852~1853,, Probably in '53 as a result of the '52 elections, the question becomes what States, make the CSA.
An earlier Civil War seems rather implausible. Without such catalysts as "Bleeding Kansas," Harriet Beecher Stowe's
Uncle Tom's Cabin, the Republican Party/large Free Soil Movement, and a more vocal, more organized abolitionist movement (although certainly the call for abolition was significant during the later 1830's into the 1840's), there isn't really a large enough spark to blow the whole powder keg.
Now, maybe you could go out on a limb and say the South seceeded as a result of the Tariff of Abominations/Nullification Crisis or the successful inclusion of the Wilmot Proviso into the budget, or maybe even a radicial aftermath brought about by the failure of the Compromise of 1850, but the premise would certainly have to be well developed.