The US is just late to the game with regards to the 6.5mm cartridges...it took us a while to figure out what the rest of the world already knew...the 6.5 bullets are beast slayers - elk, moose, mule deer etc. they over-perform.
So is a 223 on deer at 500yds. Doesn't make it the proper tool for the job.
And no, we aren't late to the game because they do nothing special. The 6.5 bologna is no different than Hornady's zombie ammo. It's a marketing induced fad.
The citizenry of the US has much freer access to more calibers, and that has been the case for some time. If the 6.5 was the holy grail Hornady and others try to make it then it would've caught on sooner.
I'm a believer in "to each his own", but I'm not going to buy into the idea that a cartridge filling a marketing niche is the end-all be-all for shooting, especially elk hunting.