It's not only dense but the scale is far larger than most European cities. Only Asian and South American cities outclass the insanity that is LA. Until you've been there it's hard to appreciate the scope of it.
https://en.wikipedia.org/wiki/Greater_Los_Angeles#Urban_area...
This isn't a size measuring contest. I think Europeans forget how _young_ America is. That's the only unique part of this country. Give us a few thousand years and we'll be on par.
Looking at the population of greater Melbourne has you looking at suburbs like Werribee, Frankston, Boronia, etc., which everyone would consider as a part of Melbourne (suburbs, outer, but very much a part of the core).
On the flip side, the "Seattle Metropolitan Area" consists of:
Mt Rainier. Bainbridge Island. Glacier Peak in Mt Baker Snoqualmie National Forest. Mt Vernon. Olympia. North Bend.
No Western Washingtonian is calling any of those locations "a suburb of Seattle".