I'm in SW Mo and they're fairly rare here. Most that do well are from generations raised here. I have 2, both are grade cows. I'm just a hobby breeder so I don't have the same focus as most of you. I have these cows because I just like the type so I understand the desire to find out if they would survive in more northern areas. I'm sort of in the middle with the weather. We don't get "as" cold as the northern states but it's still cold. Mine have some loafing sheds at the barn to get out of the wind and they can bed down where it's not wet. They also have the horses and they all tend to stock close together then. We get pretty hot weather too, with humidity. Not for as long or as bad as the deep south but hot.
One of my cows, a heifer with her first calf born a week ago, looks American Brahman. She's grey and her coat is near white in summer and thickens up a lot in the winter and it's darker grey. The other cow is a 5 yr old. She was born and raised in the area and I recently bought her. She's got a lot more ear and thinner skin. She looks more exotic, like the Indo-Brazilian type.
I'm pretty sure that when there are several generations of cattle bred and raised in an area, they eventually acclimate. Those first years would be tough but so would the survivors.