Japan was the example that stood out to me. (It's where UNIQLO is from.)
I'm 5'11"/180cm with US11/EU45 feet. They didn't sell boots that fit me in Japan. I got a deal on an "XL" jacket that the salesman insisted I buy, because I was the only person to have ever come into the store that it fit. (It's the only thing I've ever worn labelled "XL.")
same problem in China, usually the biggest available shoe size is 44, it improved a bit, but it's still lottery, I usually buy 46 in Europe, I was this summer in China, bought relatively cheap shoes online knowing it will be lottery and result didn't surprised me: 46 size shoes I received were more like 44-45 47 size shoes were actually like 47
in the end I have one pair of shoes which is fairly tight and other pair which is very loose, but got used to that, easier than tight one
and I tried to read reviews where people describe how accurate are the sizes for sizes in XL, I am quite skinny and very tall so I end up with something like 3 or 4XL to get ordinary size
btw. wife got used to European sizing where she buys XS or S size and she had very bad surprise after shopping in China where she found out she is now by Chinese sizes considered more like M or L since those XS and S Chinese sizes are pretty much for small girls :-))
I'm pretty much the same size as you.
I am a 4XL in China (or was, when I was there last) and a S in the US.
That blows my mind.