Most Thom Browne stuff including tailoring is made in the Comme Des Garcons factory in Japan now and has been for the past few years. I don't think I've seen any made in USA tailoring items in quite a while. Shirts are Garland shirt factory I believe (the shirts seem to show up with the Brooks Brothers outlet resellers). Some knits made in Ireland / Scotland and shoes are made by Sanders now (used to be Tricker's). Sunglasses are by Dita.
Shirts are good quality, suiting is in line with say Southwick so really not priced too well unless cut works perfect for you and you want tri color grosgrain everywhere and working buttonholes.