Kerry Roberts is the owner of The Bicycle Company, the parent company of Allanti Bicycle Company, the Bike Pedlar, and The Jolly Cyclist in Nashville, Tennessee. He also provides consulting services to the bicycle industry. Most of the information provided here can be cross-referenced with Bicycle Retailer and Industry News, the definitive trade publication in the bicycle industry.
The bike industry has a few secrets. And one of those secrets is where your bike is made or who actually made it. The bike companies like it that way because many of them rely upon the same factories to build their bikes!
The big picture is pretty clear: most of the bikes sold in the U.S. are made in China or Taiwan by a handful of manufacturers of which Giant is the largest.
Generally speaking, low to mid level bikes are made in China and mid to high level bikes are made in Taiwan.
Bikes are produced in other countries, but Asian factories probably produce 95% of the units sold in the United States. Incidentally, the "big three" (Giant, Trek, and Specialized) account for almost 80% of all bikes sold in U.S. bike shops.