The point was mainly about Oregon which the map has as terra nullius. In OTL it was claimed by the US, Britain, Spain/Mexico & Russia. In OTL, Spain abandoned the area North of 42N in the Adams-Onis treaty. But with a weak US, Britain, Russia and Mexico will all claim the region, and 42N will have no significance. I think the British will claim Oregon and extend the territory south of 42N.
In regard to North Louisiana, the US ITTL seems rather weak. All countries only obeyed treaties when it suited them. In the 19th century, the Anglo population was growing rapidly. In OTL significant areas of the Mid-West were settled by Yankees. The New English would be settling territories further west. It would be easy to foment an uprising in North Louisiana and claim that the American Union couldn't control the territory and that it should become a British or New English protectorate. Mishigama could be given a bit of it.