Indeed. A good read, though, and thank you for sharing it.

Here is advice from Stoeger to 1939 era American shooters regarding the 8mm:

From the Gun Digest article:
One would think a cartridge with that kind of pedigree would have a bigger following in the United States. I do realize that if my only exposure to a cartridge were via it being shot at me, I wouldn’t like it, no matter how well designed it was. Thus, I can forgive America’s Greatest Generation for snubbing its nose at the 8mm Mauser. Still, there are plenty of other reasons the 8mm Mauser (and, honestly, all 8mm-caliber cartridges) doesn’t do well here.

“In my opinion, the 8mm never really thrived in the United States because it didn’t really do anything the .30-06 wasn’t capable of doing,” said Zach Waterman of Nosler Ammunition. “The .30-06 was also the cartridge most members of the military were familiar with at the beginning of the last century; and, in my experience, people generally stick to what they know.

I would add, after the last sentence above, that one cannot overestimate the stubbornness of the American buying public, or of we 'Yanks' in general. Consider that those of us who attended school in the 1970s were told that the U.S. was in the process of converting to the metric system of measurement by 1983. I can recall some Mobil gasoline stations in the Los Angeles area selling fuel by the liter (for a very short time), and a few other attempts at change, but it seems the only ones that 'stuck' were liquor, 'soda pop', and bottled water. Otherwise, we happily confuse ourselves with an antiquated system of teaspoons, tablespoons, cups, gallons (U.S., not Imperial), ounces, pounds, acres, inches, feet, yards, and the whole bloody mess.

Time Article - Metrification US

If you suggest to the average American that we use the metric system, and how it would simplify our lives, you're likely to be told just where you should go and what you should do upon your arrival. Ask them to make change for a dollar without using 'quarters', though, and they're using the metric system without knowing. One Dollar = ten dimes = one hundred cents. When the coinage law originated in 1792, ten dollars equaled one (gold) eagle. Half dollars, quarter dollars, and half cents (minted until 1857) were used to make change for the Spanish Dollar ('pieces of eight') upon which the U.S. Dollar was based - twelve and a half cents being 1/8 dollar or 'bit' (two bits, four bits, six bits, a dollar...). The first U.S. President, that George Washington fella, was for the metric system as would be Elihu Root, Thomas Edison, Herbert Hoover, and General John 'Black Jack' Pershing among other notables.

I digress.

For decades of the 20th century, U.S. collectors and enthusiasts could find rare Oberndorf Mausers, Mannlicher Schoenauers, and other 'metric' arms at gun shops and shows being sold 'for a song' as few potential buyers wanted to deal with those 'funny foreign calibers' about which they knew little and cared less.

For those who did care (in 1939), Stoeger offered these: