There were only a few issues I had when riding. I seemed to accidentally hit the left shift button inadvertently switching to the small chainring while descending in the drops. Also I didn't like that both left FD buttons functioned the same. I'd prefer to have one button dedicated to the small chainring and the other to the big chainring. Without auto trim, it's hard to hear if the chain is rubbing on the FD or not especially when listening to music. The LTwoo grips are a bit too narrow for my taste, I tend to prefer beefier grips. The LTwoo hydro brake calipers work fine, but they're definitely heavy, I might swap them out later on for some lightweight calipers.

I must be lucky/special.

Has anyone written the 2 sellers and asked why they can't/wont sell to customers in the USA?  Since one of them sold one to me, perhaps they can be convinced to ship to the USA.

They are all same. I bought different brands and noticed that the lockring on which brand name is printed comes in its own little pouch sticky-taped to main cassette body. One manufacturer is producing those cassettes and ZTTO, Wuzei, Goldix, Sunshine just add brand lockrings on top and make it theirs. Those mid range lightweight cassettes are really good. I am yet to try scary light cassettes like Riro branded.