I think the key to high sales in the US is to put old reliable and mature technology
on the market. Americans in general don't seem to like product development.
I think several big Swedish companies have been a little bit too fast launching new products. It's deeply rooted in the American culture.
Take a car for example. Americans (at least in Texas) drive cars like Ford F250. A European guy would never ever ever buy a F250. It lacks the Adaptive Cruise Control, Passive Kayless Entry, On Board Diagnosis System, Tire Pressure Monitoring System, further it has a V8 and huge fuel consumption.
Motorcycles: Here, you don't drive a Harley unless you
are a criminal. Why drive a V2 1100cc vibrating monster with merely 60hp when you can buy a smooth running Honda/Yamaha with 180hp?
One can almost think that the less technology, the better. That could be the answer to the MS290 sales. The average American has the following setup: F250, Harley and MS290
My summary would be that cultural differences have a higher influence on sales than performace and art of engineering (260 vs 346).