Probably would need to do some research for some owner satisfaction surveys and cost of ownership comparisons to reach any factual assessment.
Without that info handy, my opinion is that perception is based on two things: National Pride and “you-get-what-you-pay-for”.
Many European vehicles are priced higher than American vehicles. Some of that is due to labor rates, raw material availability, etc, but pricing is also demand driven. Europeans generally have a stronger sense of nationalism than Americans.
It also depends on which cars we’re talking about.
German premium vehicles have been viewed higher than Cadillac, until only recently.
VW’s have a hit or miss reputation.
I don’t think Fiats rate better than American cars. (Ironically, I’ve compared Fiat as the European Chrysler, before all the bankruptcy issues.)
I think European sales of American brands have as much to do with the ‘peans desire to purchase local, than the quality perception of the vehicles.
But, that’s just my two cents. Maybe someone could post some links with factual information on European owner quality surveys or something to that effect.