"European pessimism" is this weird common knowledge about the decline of Europe. It's been written about in I, Robot. There is population decline but their GDP numbers look on-par with the United States.
It's the major/minor events rather than numbers that seem to push this mindset of inevitable decline.
Is it bad government policy? Or culture?
To extrapolate that to a decline of Europe in terms of "European pessimism" is... Quite a leap.
Even more as there is no definition of what "decline" you are meaning here, if it's for green technology I can definitely tell there isn't a decline in Europe, if it's cultural that is a much bigger topic (and much fuzzier) to talk about.
When I lived in America, Honda was much more of a trusted brand there. Detroit went after them hard via the Takata defect, so I’m not sure about now.
Some degree of protectionism is expected, of course. I mean, you won't find anyone driving a Ford or Chevy in Japan except as a novelty. But there is a line which, when crossed, gives the impression of desperate anti-competitive measures. Everyone has to decide where they draw that line, I guess.
Honda leaving Formula 1 will have zero effects on the amount of investments in Europe, not to mention it won't have any significance regarding companies reducing investment in Europe.