I think the fat:protein ratio depends heavily on how much you cook it. Crispy bacon has most of the fat cooked out of it. It may not be much protein, but it's not much of anything relative to its original weight.
This is all for streaky bacon of course. Back rashers, middle rashers, or Canadian bacon indeed are mostly protein, as the back rasher, which is half of the middle rasher, or the same chunk of meat that is cured for Canadian bacon, is pork loin (the streaky portion is pork belly).
I wish middle rashers were available here. Though I'd settle for more back rashers as back rashers + streaky bacon = middle rashers. It'd make full English breakfasts a lot easier to make right. Not that the bangers and black and white pudding are the easiest to come by either...