lol, pretty much every mobo company assembles their PCBs in Asia.
Some plants will have more consistent quality or higher-precision standards than others, regardless whether they're located in Taiwan or China or the USA or wherever. Mass-produced electronics always produce a small percentage of defects, and the odd unit sometimes slips through QA, it's improbable but not impossible for your particular piece (or even an entire production run) to be imperfect. If your unit is a defect then you qualify for an RMA replacement.
I've never personally seen an Asus mobo with defective SMT processing. Asus invests a lot of extra effort into assuring their ROG-branded products are cosmetically flawless, so I expect they put just as much extra effort into assuring these products are electrically flawless as well. I think Asus is always interested in identifying (and correcting) any plants or processes or products which fail to meet their standards. This is exactly why I choose Asus when buying certain products, but of course I would expect them to replace a substandard product.
And most consumers have little control (or even the means to identify) exactly which facility made their products. You buy a part and you see it's "Made in Taiwan" or "Made in China" or whatever, and it shouldn't matter where it was made so long as it complies with the standard.
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