that is factually wrong; a few products that come to mind
aircraft (eg Boeing)
tractors and agricultural machinery (eg John Deere)
gas turbines
automotive and automotive suppliers (gm, ford, chrysler - even the europeans and japanese manufacture in the US (bmw, merc, vw, bosch, zf, siemens, toyota)
medical equipment
pharmaceuticals
etc
while manufacturing did in certain sectors decline over time, i do think the USA is still the single biggest manufacturer