Some of the best road and mountain bikes are made in the USA. Trek of Waterloo, Wisconsin, pioneered carbon fiber frame construction. Specialized bikes are made in Morgan Hill, California and are found in pro pelotons around the world. Other manufacturers include Cannondale of Bedford, Pennsylvania, and Le Mond Bikes of California.
Note: The most popular brands of components found on bikes are not made in the USA. Shimano components are made in Japan and Campagnolo components are made in Italy. SRAM is a U.S. based component company but many of their products are made in Asia or Europe. Some of the low-end bikes from the manufacturers named above are made in Asia. Check the label on any bike to determine where it was manufactured.
This article contains comprehensive information on where each bike brand is manufactured.