I've been reading Tyler and I read McAfee.

Cowen says some interesting things but I don't think he makes the best case for technological unemployment; not sure what you mean by McAfee - Brynjolfsson is the lead author on Race Against the Machine, not McAfee.

I'm not sure you really address the central point either; why can't the disemployed people find new jobs like in the last four centuries,

As my initial comment implies, I think the last century is qualitatively different automation than before: before, the machines began handling brute force things, replacing things which offered only brute force & not intelligence like horses or watermills. But now they are slowly absorbing intelligence, and this seems to be the final province of humans. In Hanson's terms, I think machines switched from being complements to being substitutes in some sectors a while ago.

and why did unemployment drop in Germany once they fixed their labor market, and why hasn't employment dropped in Australia, etcetera?

I don't know nearly enough about Germany to say. They seem to be in a weird position in Europe, which might explain it. I'd guess that Australia seems to owe its success to avoiding a resource curse & profiting heavily off China in extractive industries, along with restricting its supply of labor.

(And note that anything along the lines of 'regional boom' contradicts ZMP and completely outcompeted humans and other explanations which postulate unemployability, not 'unemployable unless regional boom'.)

ZMP is 'marginal'; if the margin changes, ZMPers may change. During booms, a lot of margins might change. And even factors like human capital can change in importance: you can hire more dishonest employees if you switch to automated cash registers which they can't easily steal from. Or even the most dishonest evil wretch can be profitable to hire to stand on the sidewalk in a costume if you're in the middle of a real estate bubble.

Why is the IQ 70 kid not able to do laundry as so many others once did earlier, if the economy is so productive - shouldn't someone be able to hire him in his area of Ricardian comparative advantage?

Ricardian comparative advantage isn't magic pixie dust; it doesn't guarantee there's anything worth hiring him for. Another example: imagine you have this IQ 70 kid who can do laundry - I personally don't know how to do laundry well for anything but my own clothes and would ruin someone else's stuff, but let's assume you spent a few weeks training this kid how to do laundry, how to read the tags, separate clothes correctly, treat lingerie differently, not to mix bleach and chlorine, properly treat the different kinds of stains etc* - what makes you trust him with your laundry? He can be impulsive, short-sighted, not understand other peoples' emotions or responses. Well, what can he do with your laundry besides clean it that's so bad? Here's a random thought: he could masturbate with your underwear. Question: how much money do you think a random woman would pay to know that the guy doing her laundry is not fishing out her lady-things and masturbating with them? Ask the nearest women, if you dare, how much they would pay. Even allowing for CFAR/MIRI people almost completely lacking the purity moral axis and reasoning consequentially and being highly deviant compared to the general population, I bet the figure is non-zero...

* and until you've actually tried this, don't assume I'm exaggerating here. You live in a high IQ bubble.

Again, the economy of 1920 seemed to do quite well handling disemployment pressures like this with reemployment, so what changed?

People had many fewer clothes in 1920, for starters: the task was intrinsically simpler. Here's an interesting quote:

In 2008, Americans owned an average of 92 items of clothing, not counting underwear, bras and pajamas, according to Cotton Inc.'s Lifestyle Monitor survey, which includes consumers, age 13 to 70. The typical wardrobe contained, among other garments, 16 T-shirts, 12 casual shirts, seven dress shirts, seven pairs of jeans, five pairs of casual slacks, four pairs of dress pants, and two suits—a clothing cornucopia. Then the economy crashed. Consumers drew down their inventories instead of replacing clothes that wore out or no longer fit. In the 2009 survey, the average wardrobe had shrunk—to a still-abundant 88 items. We may not be shopping like we used to, but we aren't exactly going threadbare. Bad news for customer-hungry retailers, and perhaps for economic recovery, is good news for our standard of living. By contrast, consider a middle-class worker's wardrobe during the Great Depression. Instead of roughly 90 items, it contained fewer than 15. For the typical white-collar clerk in the San Francisco Bay Area, those garments included three suits, eight shirts (of all types), and one extra pair of pants. A unionized streetcar operator would own a uniform, a suit, six shirts, an extra pair of pants, and a set of overalls. Their wives and children had similarly spare wardrobes. Based on how rarely items were replaced, a 1933 study concluded that this "clothing must have been worn until it was fairly shabby." Cutting a wardrobe like that by four items—from six shirts to two, for instance—would cause real pain. And these were middle-class wage earners with fairly secure jobs.

There were many more jobs suitable for the mentally handicapped, like agriculture, which was far less automated and scientific than it is now.

Maybe eventually AI will disemploy that kid but right now humans are still doing laundry!

Certainly, but to compare with 1920, laundry got way easier with the invention of washing & drying machines (I spend more time folding my clothes and putting them away than I do 'washing' or 'drying'), and we value our privacy way more than we used to, one of the luxuries of the rich. Even drycleaning is more complex than it used to be, as the process is evolved to be more environmentally friendly, among other things.

Quick question: To what extent are you playing Devil's Advocate above and to what extent do you actually think that the robotic disemployment thesis is correct, a primary cause of current unemployment, not solvable with NGDP level targeting and unfixably due to some humans being too-much-outcompeted

See the sibling comment's link. I am of mixed minds about it, but I think your counter-arguments are bad. I don't know how much of current American unemployment is due to it but if it exists, I think it's pretty much insoluble since there are no more remaining IQ boosts left like iodine, the Flynn effect seems to be hollow gains, and so on. We're basically stuck until some miracle happens (AI? Hsu's embryo selection?), and so America would benefit from serious discussion of things like Basic Income and consolidating the current patch-work of welfare which encourages things like fraudulent disability.