The Anglo settlement of Texas- there's no reason to butterfly that out- it still happens at some point, maybe a few years later , but it will happen.
A rump US without New England will be looking south more- especially if it's more of a slave country.
I would say there could be a reason, but I agree it was innevitable. Still, circumstances are key. It took off mainly when Moses Austin brought the Old Three Hundred. And that happened when the Panic of 1819 forced him out of his bank business in Missouri, if I remember correctly. Is all that still on schedule? And also, interest is bound to be divided now. Southerners were mainly the ones who moved in OTL. Would the lack of a Missouri Compromise Line now entice them to move instead north-northwest? The scenario calls for the US to still have the Lousiana Purchase region, more or less. So they still have a north to look to. Can interest now be in moving into the plains rather than Texas? It's bound the interest to be divided, in any case.
And that's not assuming the country doesn't fragment further when the south tries to impose slavery country-wide, weakening it further. Which I guess in the proposed scenario it didn't, but I would think it might not have gone without a fight or so. Would the remaining North really fold to the South without a fight?