What's the situation in the US? You're obviously not talking about direct cost,

    Mean house price: 
       London: $753,793 USD
       USA: $369,147 USD

    Average rent per month:
       London: $2,992 USD
       USA: $1,699 USD

Or being cramped into small spaces,

    Average home size:
       London: 705 sq ft.
       USA: 1,800 sq ft.

Or homelessness,

    Estimated homeless population (% of total population):
       London: 2%
       USA: 0.2%

Perhaps you are referring to comments on HN?

    Annoying comments about housing posted on Hacker News:
       London: Not seen
       USA: Way too many

I think they meant comparable (i.e. desirable, world-class) cities in the US. You want to compare London to cities like Los Angeles, New York, etc.

That wouldn't be a US situation, then, only a New York, or Los Angeles, or wherever situation. But it clearly says it is a US situation.

Why do you get to cherry-pick London only then?

Because the original comment that was replied to cherry-picked London and compared it to the US. Start from the top.