I have a Doyle StackPak (2006) and a Doyle Headsail (2007), one bought in TX, one in MD. Both sails were made in the Caribbean (I forget which island). Perhaps they've changed how they do things, but that was the procedure when I bought mine. I've never heard anything about their sails coming from anywhere in Asia.
PB, things have changed a lot in a few years..
Excluding exotics (like 3DL) for a sec, essentially there are two types of sail lofts: the Value-Add type stitch their own; the Importer type order the completed sail from Asia. Fortunately the first type are in the majority still, but it's market-driven so who knows what the future holds.
The key to this is to find out where they get the cloth. Up until the early part of this century, sailmakers would buy rolls of cloth (typically only Dacron, Mylar and Kevlar back then) in various grades, cut the panels in-house and stitch up, but that means stockpiling large amounts of expensive material in the hope that someone will want a sail made from what you have to hand and with the advent of new fibres (Carbon, Vectran, etc.) stockpiling a vast range of expensive 'raw material' doesn't make economic sense.
Around 5 years ago now, with the purchase of some Australian and European technology under FTAs with moronic governments, Chinese polyethylene manufacturing shifted up a gear. Sailmakers the world over then got smart: "Why stockpile large amounts of material when we can order only what we need on-line using 'just in time' principles?? We'll need less storage space, overheads will go down and we can (unless we're greedy) pass the savings onto customers." So.. if you were to go into your local modern loft now and order a new sail, they order the cloth you want, usually in computer-cut panels, directly from the manufacturer - and usually from Asia.
Since the art of good sailmaking is in the way the panels are stitched together, good sailmakers retain that expertise in-house. That's why, over here at least, many people will only buy racing mains and headsails from a local loft of their choice - but where sail shape is less critical they buy spinnakers from a cheaper Importer (eg. Taskers), knowing there are is little or no difference in the quality of the cloth just the way it's stitched together, since the plastic all comes from the same place... just to the north of us.