"Answer: a lot less than a drunken typical-weight in a car colliding head on into an oncoming car in the car lane."
- it's also a lot less than a big truck so while very well written, your point is irrelevant.
"- the oncoming bike actually collide."
Yes, that is the assumption otherwise we wouldn't be talking about it
"- the drunken biker is on the bike in the first place."
Also yes, otherwise it doesn't count towards 'riding drunk'
"You can also use the bike as a walking frame if you're that much fucked up"
Well, yes and that's fine. We are talking about drunk people riding here. I don't understand why you continue to mention anything other than drunk people riding bikes as that is the discussion.
"Whereas death by drunken cyclist are so seldom here around (Europe) that they aren't considered a real problem."
In comparison, sure. The same could be said of the number of children that are crushed by out of control skiers coming down the mountain. A relatively low number - but still a problem to be avoided and not ignored.
"I literally haven't heard of dead drunken cyclist around where I live"
20 percnet of bicyclists killed had blood alcohol concentrations of 0.08 g/dL or higher.
"bicycle accident tend to be a lot less deadly"
Less deadly is not not deadly.
"which is the case in North European cities with a decent network of bike lanes"
I live in Paris which has a decent network of bike lanes but no, it is generally not the case as the bike lanes are often not separated from the road.
"- taxi can cost a lot,"
Which is why I said " if you can't afford the taxi then don't get drunk."
Walking your bike when you're drunk is perfectly acceptable.