Later in Washington D.C.
In all his years in Washington the Texan ambassador had never felt as small as he did under the withering gaze of President Abraham Lincoln. Word had somehow leaked about President Seguin's threat to the Confederacy, and it hadn't taken long for him to be summoned to the executive mansion to, in Lincoln's words, "clarify the position of the Republic of Texas," but in plain english explain if his country had a death wish. So for the past seven minutes he had calmly, well as calmly as he could when two blue clad youths kept glaring at him, reiterated what President Seguin had told him in the telegram about it being an empty threat, and that it had simply been stated to get the Southern rebels to respect the international border. Lincoln seemed to accept this, but it would be a good many months before anyone could laugh about this.
Ok, this probably didn't happen, but I imagine if anyone in Washington has found out they aren't happy about Seguin's threat.
If things go well for Texas I could see them annexing Sonora and Chihuahua after this war. I'm not sure any other Mexican territory would be a good idea though as Texas is still a bit on the thinly populated side itself (Two million at this point?), and I think Rio Grande may have been bitten a bit to hard by the pan Mexican nationalism bug to make them an easy pill to swallow. Regardless, Texas at a minimum is going to come out of this intact, but who knows about the other combatants.
I'd watch a tv show set in this universe.
Fingers crossed.
Anywho, not sure how long it has been since I've commented, but I'm still here, and good updates.