Fudge Kangaroo courts Harry at the start of OOTP, his wand is snapped and he is expelled from Hogwarts. Fleur, who happens to be at the Ministry for some Gringotts paperwork, stumbles across Harry and offers him another option as favour for saving her sister. Pulling some connections, Harry is enrolled in Beauxbaton and finishes his education in there. After all the French are always happy to stick it to the English. Harry stays in touch with Fleur, who returns to France after a year or two, the pair reconnects and they quickly begin a romantic relationship. Voldemort never "outs" himself since the DoM doesn't go down, he is content to stay in the shadows, building his forces and influence. After graduation, Harry, given his native English skills, is offered a position as Marshall in French Louisiana (everything between the Continental Divide and the Appalachians would be magical French). It is barely settled by magical Europeans and generally run by natives. Basically, Harry's job is to keep an eye on all sorts of magical creatures hiding in the area, making sure no Americans (especially no Muggleborn) violate the lands of the local tribes and that the law is maintained. He is partnered with a young native woman under a grumpy old Frenchman, the sheriff, much to the annoyance of Fleur. Fleur ends up moving to French Louisiana as well because the long distance relationship isn't working all that great and, after a string of disappointing relationships while she was in England, needs more than the odd visit once a month and a few letters. Which leads to Fleur being dragged into all sorts of shenanigans, especially once Voldemort tries to expand his influence past the Atlantic. You could even spin this into a Spain vs France in America, with Voldemort rousing various nominally Spanish tribes and creatures in that area. There's bound to be a bunch of giants in the Rockies, and plenty of native mythology to draw magical creatures from.