Many of those cities are compromised of enormously large areas though. Chongqing is larger than the country of Austria and has a population density of 390 people per square km. London has a population density of 15000 people per square km.
There are still a lot of big cities and huge city centres but the Chinese meaning of city often includes the metropolitan area plus rural hinterland.
It sounds like you may be comparing the population density of a large, diluted area and not the downtown areas alone.
It doesn't get much denser than downtown Chinese cities, they have specialized in high-density mega-sized apartment buildings.
Even large US downtowns are dwarfed by the average Chinese city downtown flush with LED skyscrapers. They have way more people and manufacturing than other countries so it shouldn't be too surprising.
There are still a lot of big cities and huge city centres but the Chinese meaning of city often includes the metropolitan area plus rural hinterland.