Here is the thread you mention, I think.
Yeah that's the one. One of those rare instances where 67th Tigers' Britwanking and reverse wanking of the U.S. with the exception of that exceptional American McClellan didn't keep him from putting his knowledge of the era to reasonably unbiased use.
The basic strategic situation strongly favors the U.S. By 1865, Max has already pissed away what goodwill he had from anyone, and only the French troops are keeping him on his throne, and they were steadily losing against the Juaristas. The rate they were losing at is about to get much worse as all the extra weapons from the demobilized American regiments make their way South, and we are only talking OTL. Nappy already has more troops than he can afford tied up in the Western Hemisphere and the situation in Europe is about to get much more fluid as Bismark's machinations proceed.
Nappy would be insane at this point to do anything else other than back down as OTL and give Max up for lost. If on the other hand, he does go insane, pretty much his only option is to go for a coup de main and hope to win quickly then get his troops and ships home. This means an all out attack to sweep the USN from the seas and take Key West, then follow up with a loose blockade, which depending on how far the USN's demobilization has gotten, may take up to half his modern seagoing fleet or more. Perhaps follow up with raids on the coast and attempt to incite insurrection in the South and hope a war-weary U.S. is willing to give in quickly. Then pump a few more corps into Mexico and drive Juarez underground.
Full success means a nice shot of prestige, which unfortunately won't last long, as partisans continue to harry his forces in Mexico and U.S. still supplies them under the table no matter what the Peace Treaty says. Sooner or later, those troops will be needed at home at which point Max collapses and any troops left may face a Dien Bien Phu.