Over six decades the US guitar market shifted from 100% American made to largely Asian imports.
1960s: cheap, low quality Japanese and Italian imports arrive due to the surge of guitar sales caused by the Beatles
1970s: A few US companies start importing Japanese made guitars...Gibson turns Epiphone into an import line, Martin starts Sigma, Guild starts Madeira. Ibanez starts offering high quality MIJ copies of Gibsons, Fenders, Rickenbackers, Martins, etc. Late in the decade Hondo starts bringing in Korean copies but loads them with US DiMarzio pickups. Peavey brings out the T60 and T40, undercutting Fender and Gibson prices by more than 50% but still 100% made in USA. Ovation starts the MIJ Applause series. Companies like DiMarzio, Mighty Mite, Schecter, etc. start selling parts for "hot rodding" guitars but also making it easy for foreign builders to get high quality pickups, bridges, tuners, etc.
1980s: Success of Hondo opens up market for other importers of Korean instruments (Memphis, Cort, etc.). Fender starts making guitars in Japan for the Asian and European market. Then they bring them to the USA under the Squier name. They also start making some amps in Japan (Sidekicks, etc.). Gibson revives Epiphone with high quality Les Pauls. Gretsch is the first US comapny to go completely overseas. Fernandes and Tokai start selling high quality copies of Gibsons, Fenders and even Alembics! Other quality Japanese brands start arriving like Yamaha, Aria, Kawai, etc. A few brands like Washburn and Hohner are revived under new owners and import Japanese or Korean guitars. Steinberger starts lawsuits against Japanese copies of their bridges then offers licensing deals to Hohner and Cort. Ibanez pivots from making copies to their own designs, including the very successful Soundgear basses. Mid-decade CBS sells Fender, closes the Fullerton plant and all instruments except the Vintage Reissue series are made in Japan. No US made Fender basses until the 1990s. Boutique builders Ken Smith and B.C. Rich start import lines. Seymour Duncan, EMG and Bartolini start licensing Asian versions of their pickups. Ironically, while US EMGs ahadd all been active the Asian versions were all passive.
1990s: Fender now has factories in Mexico and starts importing Squiers from Korea as well as Japan. Other import lines start switching to Korean suppliers to save money. Danelectro is revived. Hofner starts selling Asian made Beatle basses. Towards the end of the decade under extreme market pressure, Peavey starts moving some guitar and amp production to Asia. OLP imports licensed copies of Music Man guitars from China. Gibson starts up Music Yo as an Internet dealer to sell Korean versions of Steinbergers, Kramers and Tobias.
2000s to today: Ampeg moves all amp production to Vietnam, then gets bought by Yamaha. Guitar manufacturing shifts from Korea to China and then Indonesia. More brands are revived with Asian guitars and amps: Supro, Acoustic, D'angelico. Guild and Ovation move completely to imports. GK starts a new line of MB combos made in China, but after problems, they bring production back to the US for the MB-II series at higher prices. Gibson and Fender start shutting down many of the brands that they had acquired...SWR, GenzBenz, Ovation, Kramer, Tobias, Oberheim. Peavey acquires Trace Elliot. Sadowsky starts importing basses from Japan, then sells the brand to Warwick who starts making them in China.
The thread running through all of this is pricing. Imports were necessary to combat rising costs of US manufacturing.