Some cities such as Boston and Seattle have been lowering that a lot. Seattle seems to be moving to 25 MPH (40 kph) everywhere. Boston has lowered the default from 30 to 25 MPH (50 to 40 kph), likewise Somerville MA. Cambridge MA has reduced from 30 MPH to 20 MPH (32 kph) on local streets and 25 (40) on arterials.
OTOH Japan is 30 kph (18 MPH) for residential (often one-lane, one-way, no sidewalk, there's also an option for 20 kph (12 MPH)), 40 (25) for urban 2-lane roads, 50 (30) for 4-lane roads, or no more than 60 (36 MPH) on divided 4-lane roads with low pedestrian activity. Nothing with at-grade intersections, or with pedestrians and cyclist access, can be faster than 60 KPH.
So Japan residential streets are slower than typical US school zones. Most major streets are no faster than typical US residential streets.
Wiki says the Dutch urban default is 50 kph, but 30 kph residential is common, and "home zones" may be as low as 15 kph (9 MPH), but some 4-lane arterials are posted at 70 kph (44 MPH)
Makes a big difference in crash safety, but also in car noise: slower cars are quieter, and probably fewer in number.
Canada defaults to 50 KPH, but Montreal lowered its streets to 30 residential, 40 arterial.
Australia seems similar to the US, though with pushes to 40 kph in central business areas.
This road in Osaka, an six lane (or here, eight) divided road with barriers to discourage pedestrians (and prevent them from jaywalking)... is 50 KPH (30 MPH). It comes out of giant intersection, which has a 40 kph (25 MPH) sign posted. See the DW comments at https://mindstalk.dreamwidth.org/582754.html#comments