> I don't think you realize just how much higher the median income is in the US and how much space the typical family has.

You really don't realize just how low the median income in the USA is. It's $45k for the median full-time employed individual¹, compared to $39k (£29k) for the UK². You can put the figure in pounds into https://listentotaxman.com/ if you'd like to go further with this, and think of taxes, healthcare etc.

I think your argument still holds, but only for part of the middle class or above. (There's an income distribution table on the Wiki page.)

> …walkable city…

Very few people advocate for only dense, apartment-style housing. They are actually advocating for the choice, to be allowed to build something that isn't a large house with space all around it. This is forbidden by zoning rules in much of the USA.

In a European city, and I'll pick Copenhagen since I live here and it's often cited as one of the best in these arguments, you find apartments of various sizes in the city centre (plus a very few extremely old, extremely expensive houses). As you travel away from the centre, there's a mixture of apartment blocks, smaller apartment buildings (perhaps three apartments in a 3 floor building), denser single-family homes (e.g. shared walls with one or both neighbours), and homes with grass all around. The further you travel, the more the balance shifts to the end of that list -- though if you pass a railway station, you'll find some more apartment buildings. Shops are also distributed throughout, though they are usually nearer to the apartment buildings / stations for obvious reasons.

On [3], the part between the rough circle of water made by the rectangular lakes in the north west and the old zig-zag water fortifications in the south east is considered the city centre. You'll see the type of housing change if you zoom in, then move north, northwest or west. (South, you'll not get the same effect as you'll run into the airport or a nature reserve.) You can also search "Supermarket".

I have a colleague with a couple of children, a decent garden, a car, and a basement containing a metalworking workshop. He's still within 10 minutes walk of a supermarket, and it would be safe for a child to walk there alone.

A friend needed more space than that for her hobby, so she lives on the edge of the city. She has a huge garden (which is the hobby, part is growing food), but she also has a 20 minute walk to the station if she wants to go somewhere without driving, i.e. before and after drinking. (Or < 10 minutes on a bicycle, I assume.)

Conversely, I live in the city centre. A colleague with two children lives fairly close by, in an apartment. Our hobbies don't need lots of space, so we've never felt the need to move further out. The adults and children don't have plenty of space for big hobbies, but it's a more convenient location for other things, like cultural activities, restaurants, people living nearby.

One example of that: a friend's teenage son likes LARP. At 13/14 he obviously can't drive, but he can walk a few minutes to the station. That takes him to the shop selling foam swords and whatever in the city centre, and the locations in/around Copenhagen where LARP groups meet, mostly in the larger woods.

(And can we say man, rather than kid? He's 22.)

[1] https://en.wikipedia.org/wiki/Personal_income_in_the_United_... (First paragraph, $865*52).

[2] https://www.statista.com/statistics/1002964/average-full-tim... (2017 figure to be comparable)

[3] https://www.google.com/maps/@55.6841742,12.5866976,4173m/dat...