I couldn’t find stat for all of North America, but 70% of American adults are overweight, so most North American woman being overweight wouldn’t be that surprising.

Some of this is that BMI can be misleading. It’s based on your weight divided by your height squared. From a medical statistics standpoint, it’s better than nothing, but since it doesn’t make a distinction between muscle weight and fat weight, it can put a lot of very muscular people in the overweight column.