That may sound overly simplistic but I think there's an element of truth to it. Foreign vehicle companies needed to fight to gain market share in the US, often needing to be much better just to be compared as equals. Look at KIA recently doing so, now they're doing very well reliability wise and offer a substantial free warranty, but ask random people and they'll be described as unreliable foreign cars.
The real mystery is why Americans still buy American made cars. The foreign competition has eclipsed them for whole generations at this point, but yet demand remains.
The US imposed a 25% tax on imported light trucks and has for decades (the "chicken tax"). I think that this has resulted in a weird distortion where American auto makers focus heavily on that one more profitable market segment, and advertise most heavily on that one market segment, and have done so for generations.
There's a reason that Musk is building a Tesla truck.
Those of us “of a certain age” will remember that this is not new at all.
I can’t speculate on the reasons, but I agree about standard quality levels being higher in Japan and Western Europe; but so are costs.