Bikes are an automated machine shop event. The technology advantage that Taiwan invested in made them the best mass produced frame makers in the business. As it turns out, many of the large mainland China bicycle plants are actually investments by the Taiwaneese. Although the two countries may not get along politically, so far that has not been a problem for businessmen.

I would not worry about the quality of any name brand Asian built bike. You might have to worry a little about frame and fork seconds that show up on Ebay every now and then. Most of the Trek's and other name brand bikes in your LBS are sourced out of one or the other of the Chinas.

There have been some articles posted in BF about where particular bikes come from. Most of them are old news by now as more and more production goes there.