realy ?
I was just in Jerome ID last week , and ended up talking guns , and in Idaho Falls ID, 270's and 308's are big there , then in Three Forks MT lots of 270's and 308's there too, found no one shooting 7mm-08's but a lot of big mag,s And I have family (inlaws) in Bellgrade MT and they all hunt , Elk, Mule Deer , White Tail , Antelope, and American Bison, with 270's ,, not that a 30-06 wouldn't work , but to say in is a minimum is a strech,
Well, last time I checked which was a few days ago when I drove through it, Idaho Falls is prairie country, not deep woods with grizzly bear walking around. More antelope than bear in that area.
Three Forks MT and Bellgrade MT are in the eastern part of Montana which is likewise farmland and prairie as well. I see you didn't list grizzly bear, black bear or mountain lions all of which we have in the Idaho panhandle as well as way too many Mackenzie Valley wolves.
So, I will stick to the truth of what most up here in the Idaho panhandle talk about, 30-06 and up for their elk and bear/defense. Jerome Idaho likewise has long range shots out in this open farm land with antelope among the animals hunted there. That is not at all like the heavily forested areas up here just a couple hours below the Canadian border.
One of my friends is a .270 only hunter, but he has had ribbing for that choice for years in this area. Funny thing, he has shot more elk than just about anyone else in the area, so he gets the last laugh. As you know, the ballistics of the .270 and the 30-06 overlap in many of their loads.
I don't no anyone up here with a .308. One of the teenagers has a .243 for deer, but I am sure when he finally goes for elk, he will leave that behind. So, yes, 30-06 is considered the minimum rifle by many up here. My elk rifle is a .300 WSM and one of my other friends uses only a .300 WM. So, knowing your hunting grounds dictates what rifles are common. Once again, up here, I don't know anyone that hunts with a .308.
Lastly, for an all around rifle good for any part of the US and Canada, you just can't get a whole lot better than a 30-06 from North Carolina to the wilds of Alaska. Even though the OP left out the 30-06 option, who can deny it has earned it's place in history as well as still being one of the most popular and useful calibers today.