GOOD LUCK.
Most of the manufacturers are intentionally vague on this.
When pressed for info, an employee of Frigidaire (now owned by Electrolux, I believe) the following was disclosed.
Got that list from this website.
https://allamerican.org/lists/
Sadly, I could not find a definitive answer regarding made in USA microwaves.
Ranges – Springfield, TN
Built-In Cooking – Memphis, TN
Microwaves – China
Top Mount (under 20 cu ft) – Anderson, SC
Top Mount (over 20 cu ft) – Juarez, Mexico
Side-by-Side – Juarez, Mexico
French Door Bottom Mounts – Juarez, Mexico
All Freezer (Twins) - Anderson, SC
Large Upright - St. Cloud, MN
Stainless Tub dishwasher – Solaro, Italy
Plastic Tub dishwasher – Kinston, NC
Laundry Center - Juarez, Mexico
So, it appears that only some of their appliances (but not microwaves) are made in the USA.