Its not just the US as most last mile standards are not symmetric because they only use one line for both directions and use different frequencies for each sid

Its not just the US as most last mile standards are not symmetric because they only use one line for both directions and use different frequencies for each side (most DSL, cable, PON). So the spectrum available is limited and since most users will benefit from more download rather than upload the split is not even by choice. But like in your example the ISP can sometimes tweak how much is available in each direction and you end up with those insane differences. Where I live we mostly have symmetrical ethernet fiber, and some cable. We started using fiber long before PON came out and it never became popular here so pretty much all fiber here is 100/100, 1000/1000 or even 10000/10000.