The softest aftermarket shock/strut is supposed to be the Monroe Sensa-trac. There are many different types of the Monroes, but the Sensa-trac is supposed to offer the smoothest ride. Typically, aftermarket shocks/struts are overly firm, much firmer than ones from the dealer. Perhaps your car is tuned to ride like this and it has firm springs as well. I am not familiar with the Euro models, but I would guess they would have a firmer suspension. I know that a lot of the older Mercedes, such as the 240D and 300D typically have a soft and supple suspension, as well most of the large S-series sedans, especially the 81-91 full-size. I think the later ones may have a firmer suspension, but still comfortable.
I have a similar overly firm and harsh suspension as well on my 1993 Toyota Camry LE V6. I think the struts were replaced with performance struts. My rear struts seem OK and fairly supple, but the front struts are very harsh. Will barely press down when you press down on the front bumper. I have had other Camry's in the past and all had a smooth, soft ride. I have tested other Camrys like mine and most of those also had a soft ride. I was going to install Sensa-tracs, but someone else told me they had them on their Camry before and it was not as supple as the original Toyota struts they replaced them with. Bad news is for my car, is that the original Toyota struts are $150. each, just for the struts. Then probably $100-200 more for installation. My ride is so harsh, I have considered selling the car, instead of spending $500.+ just on the front suspension. Still, my car is still 100% squeak and rattle free on the inside, so one sign that these are very high quality cars. One good thing is that my other three full-size American cars all have a soft and comfortable suspension. Especially the Buick with "Dyna-ride" air suspension. Good luck with your suspension.
1993 Mercedes 400SEL 4dr
2012 Honda Civic LX 4dr
1972 Chevrolet Caprice Kingswood Estate 9-passenger wagon
1973 Pontiac Grand Ville 4-dr hardtop sedan
1988 Mercedes 300SEL (was mine, now mothers)