Earlier this year I had to return slightly over 20,000 bolts because the supplier sent ones that were not made to the correct hardness. The year prior I returned 5,000 bolts because the supplier did not follow the print and the shoulder was too short. But I also deal with hundreds of thousand bolts a year from China. I do not recall my American sources causing any problems in recent memory. So it can be an issue, however it is also the importer having poor quality checks.
In my personal life I tend to buy USA made, however that does not mean all Chinese products are junk. I did bend a 15/16" Chinese combination wrench, and used a Proto to take the bolt off without any issue last month. At work we sell some Chinese roller chain and bearings that is damn good, and I would buy it without hesitation, however the Chinese chain sold at retail stores is horrifying. We did some tests on various Chinese roller chains vs American made Drives and Diamond chain where some chain tested as good as American made, and others were terrible. This shows that not all Chinese products are junk, but some can be.
I do not understand why everyone has to be so defensive about China product quality. Lets all respect each others opinions, as we all come from different backgrounds.