OP here (though I don't claim any special insight, as I said).

It would be interesting to consider the differences between the Charlie Brown and Arthur Dent character archetypes.

One difference seems to me exactly the undying earnestness and optimism you mentioned: in a way, Charlie Brown and other American characters like him are simply not touched by failure (even if bad things happen to them), because of their optimism[1]. This makes them lovable: we appreciate them for this quality that we (most of the audience) do not have.

[1]: (or lack of self-awareness, in some other cases mentioned here like Homer Simpson or Peter Griffin)

Arthur Dent, on the other hand, is not gifted with undying optimism. He's constantly moaning about things, starting with his house and his planet being destroyed. This makes him relatable more than lovable: he's not a “lovable loser” (and for the right audience, does not seem a “loser” at all), he is just us, “my kind of guy” — we feel kinship rather than appreciation. We relate to the moaning (if Arthur Dent were to remain unfailingly optimistic, he'd be… different), whereas if Charlie Brown were to lose his optimism or if Homer were to say "D'oh!" to complain about big things in life rather than hurting his thumb or whatever, they would become less of the endearing American institutions they are IMO.

In American storytelling, being optimistic overcomes being a failure. In fact, you haven't failed if you still have hope.

Homer Simpson is an idiot, but he doesn't give up. That's endearing enough to hold the protagonist roll.

99% of references I see to Charlie Brown in the U.S. are as a sucker who never learns.

Also a counterpoint, but from the other side (from British Speculative fiction): Terry Pratchett's Discworld series

These books, written by a British author, are full of characters with strong wants who are roused into situation-defying action.

These books are also best-sellers on _both_ sides of the pond, and often share shelves with Adams.

He has more modern versions in Homer Simpson and Peter Griffin. But most of the failures or misfortunes they experience are quite mild or temporary, all things considered.

Only a European, and one who grew up on US stuff, fondly so, charlie brown feels very low on the exposed and perceived American ethos / values. I saw a few strips and refs .. but that's about it.

I think this is a distinction between comedy and non-comedy genres.

There are many examples of protags in American comedies who never get their way -- Party Down, Seinfeld, Always Sunny. Part of this is the need for American sitcoms to maintain the status quo over dozens of episodes / several seasons.

You rarely see Hollywood action heroes who are beset with unrelenting disappointment -- they usually go through hell, but by the end of the third act, achieve some sort of triumph.

A notable counterexample is Sicario, but I wouldn't call it a "Hollywood action movie."

As with everything else, sweeping generalizations about "culture" rarely hold up in the modern world.

I don’t know anything about Charlie Brown, but I’m not sure constant bad luck and disappointment capture the spirit of the British humour being discussed, as that can just as easily be used to describe slapstick humour. Perhaps it’s the existential futility/resignation that’s missing? Charlie Brown is a child, so they perhaps have optimistic naïveté instead (such that their failure be viewed with pity instead of kinship, which is really the distinction here).

I'd say there are more. Courage the Cowardly Dog? Very much in the lovable loser camp. The Eds from Ed, Edd 'n' Eddy also fit, but I suppose you could say that's a Canadian show.

Another counterpoint: Columbo

Charlie Brown is dying in America. Gen Z doesn't know who he is.

Most Americans wouldn't consider Charlie Brown the "hero" of his strip, they would consider him a loser who gets what he deserves, and that's the joke. He isn't cool the way Snoopy is cool.

I think the article is correct that Americans don't feel sympathy for the underdog who doesn't overcome and succeed in the end so much as contempt, due to their inborn sense of entitlement and belief that failure is caused by a lack of moral fortitude and excess of laziness rather than systemic injustice and inequality.