but the south had no such resources, unless thy invaded mexico, made peace w/ the usa, and fucused thier attentions to central america, they might cause a second civilwar, and pwn the us.
First of all, let me just say... It wouldn't be a Civil War if it were two soveriegn nations going at it. Just sayin'. ;-)
Second of all, no way in hell they'd conquer Central America. The US as a whole couldn't do it... If you take out the population and industry of the north, the CSA has no way of creating an army powerful enough to conquer that whole territory, unless it's over a huge span of time (and I don't just mean a decade or two). Over enough time, either the two countries would have another war (with the US throwing all of its effort into it, allying with with the remaining Latin American countries, or the huge amounts of geurillas that would pop up in occupied territory), or tensions would have cooled, and they'd be pretty neutral towards each other.
Third of all, the CSA attacking Mexico at the time would be a BAD idea, and there was no way it could've gotten a good enough Navy together to hop the Gulf and attack Central America proper. France was busy setting up a puppet government in Mexico. If the Rebs attacked France's new little buddy, they'd get one of their few possible European allies pissed. With France against the CSA, the new nation would be screwed.
And you're assuming the US would be idle throughout all this. If its blood enemy-turned-rival somehow managed to supercharge its industry, conquer Central America, pacify all of the many, many geurillas that would pop up in what is, if I remember my geography correctly, great geurilla territory, I doubt the US would just sit back without trying to expand or build up its industry. We might not have as much room to expand as the CS, but we have a huge head start industrially, and a huge territory with plenty of natural resources.