Not as many as you might guess. Of the players that entered the semi-finals games, I think Atletico Madrid is the most represented, followed by Barcelona. And then just Bilbao and Socieded. So 4 by my count, and none from Real Madrid.
I saw this just after reading your reply:
I don’t know whether it is paywalled, but they claim that Atlético de Madrid has been the club with the most players in the final for the last three editons of the WC.
I just went through the benches, and there is a Celta Vigo player on Spain’s bench.
Did Belgium ever fight a war against England? I have a hypothesis…
Belgium did not become an independent state in the modern sense of the word until after the Belgian Revolution of 1830. That was years after the Battle of Waterloo! Which took place in Belgium, btw.
As part of other countries like Spain or the United Kingdom of the Netherlands it did fight (or was fought, depending on how you want to see it) wars against England.
A nice video explaining the history of why and how the cards came to be used in football.
Some interesting bits, English referee Ken Aston was famous for inventing the red and yellow penalty card system, he officiated the notoriously violent 1962 World Cup match between Chile and Italy, later he was appointed the head of World Cup referees for the 1966 tournament. So he sat there in the Wembley Stadium stands, when on July 23rd, England played Argentina in the World Cup quarterfinal.
After seeing that, Ken Aston came with the idea of the red and yellow signals, originally he proposed to his wife (Hilda) that it should be arm bands in red and yellow, and the ref would point to the appropriate color,
Hilda had a better idea. She disappeared into another room, and she returned with sheets of colored craft paper. She took a pair of scissors, and she carefully cut two rectangles, one yellow, one red, sized to fit neatly into a shirt pocket. It was perfect.
Of notice that while most of the word did agree with the new system starting in the 70s, England decided not to use the card system since (only briefly until 1976, refs feared that the hooligans would be more angry at the sight of the cards 
),
It took until 1987 for the cards to be permanently reintroduced in English domestic football.
Question, how seriously do nations take the bronze-medal third-place vs fourth-place game? It seems to be sort of a consolation game to make one of the semifinalists not end their campaign on such a sad note, but are there any fanbases that do care about it?
It depends, if you are a football power you hate it and do NOT want to play it, but if you are a relative newcomer you probably think that a 3rd place, specially against one of the aforementioned powers is a great thing.
There was one exception: after Germany unluckily lost their semi-final to Italy in our otherwise very successful home tournament in 2006, we all were lucky to win the game for third place against Portugal and leave on a positive note.
I don’t know about lucky, but I like to think of it as a warning shot across Luiz Scolari’s bow that would come to fruition eight years later. 
I was thinking that this Eng Fra game would be nothing, then I read a comment over on The Guardian that suggested Mbappi could still try for the golden boot as it’s not at all certain that Messi will score in the final .
I guess an outside change that Kane or Bellingham could be in contention if France does not show up at all.
So maybe there could be some fire in this one.
Though I think that a golden boot at a WC is a welcome gratification for a player, I don’t think those players think much about it before that game. In the end, they all played to win the cup and failed.
I still remember the World Cup in the USA last time, when Bulgaria fought for the third place, but instead of striving for a win as a team as they should they only tried to make Stoichkov win the golden boot. I forgot who they played against, but they failed miserably. Stoichkov, of course, did not score, therefore he did not win the golden boot.
I can see something similar happening with Mbappé tonight.
I quite liked Stoichkov. I will not shed a tear should Mbappé fail in a humiliating fashion. May his ego suffer a big blow!
It probably depends. However, England and France have a bit of history, and so will take this game more seriously than a Yanks-Mets final or a New York-Boston one. Consider everyone thought France would win, fairly easily.
Not sure why Mbappe would be playing then. I suspect a lot of shots by him for the Golden Boot. I suspect Dembele might want a shot too, although he’s not in the starting lineup.
You cannot plan or play a game like this, with the only intent to score as often as possible, or for the team to make one player score as often as possible. That’s not how football works.
(ok, now I’m ready to experience a third place game with three goals by Mbpappé, all beautifully assisted by Olise or Dembelé, just in spite of me saying this)
I didn’t say that. But there’s a reason why the over/under betting line on this game is 3.5, when it would be 2.5 if this were the final. Yes, they are trying to win, but more aggressively.
That is precisely why Bulgaria failed. They were a good team back then, but this tactic was absurd, ego driven, foolish.
Same will happen to France if they try.
ETA:
To “experience” is a relative thing. I believe German free TV will not show this game.
And also an eye to the all time record, you never know what can happen in 4 years, the future isn’t guaranteed. I can see France just feeding him like you’d see in basketball when Kobe or whoever was trying to break a record.
That’s why I didn’t say “see” . Because I will follow it on live ticker on kicker.de.