Electronics/musical instruments/entertainment: Gibson guitars (electric and acoustic), Fender electric guitars and amplifiers, PRS guitars (Paul Reed Smith), Taylor (acoustic guitars), D'Addario guitar strings, Mesa-Boogie amplifiers, Conn, Crown, Ampeg, McIntosh, Western-Electric, RCA, Hickok (vacuum tube testers), MGM, Paramount, Columbia, 20th Century Fox, Warner Bros., RKO, Electro-Voice, Altec, JBL, Cerwin-Vega, Qualcomm, Shure, Hammond, Steinway, Baldwin, Ludwig, Slingerland, Guild, Gretsch, Ovation, Motown (records), Ampex, Motorola, Zenith, Philco, Blockbuster, Wurlitzer, Rock-Ola, Seeburg.
Transportation: McDonnell/Douglas, Peterbilt, Kenworth, White, Cummins, Detroit Diesel, Bluebird bus, Winnebago, Airstream, American LaFrance, MasterCraft, Chris-Craft, Stearman, Piper, Beechcraft, Bell, Hughes, Learjet, Gulfstream, Holley, Edelbrock, Crane, Schwinn, Moroso, Pratt & Whitney, Corvette, DeLorean, Hertz, JPL (Jet Propulsion Laboratory = space stuff), Packard, Studebaker, Oldsmobile, Model T, Model A, Mustang.
Construction/tools: Kohler (small engines), Manitowoc Cranes, American Crane, Linkbelt hydraulic cranes, Snapper, Snap-On, Stihl, Ingersoll-Rand, Case (knives), Allis Chalmers (now Fiat-Allis), International Harvester, Skil, Black & Decker, Red Devil, PPG (Pittsburgh Plate Glass), Rinker, Quikrete.
Office: 3M (also the best electrical tape), Eagle pencils, Parker Pens, Fisher Pens, Post-It, Xerox, Hewlett-Packard, IBM, Papermate, Royal, Brother, Underwood, Swingline.
Home: Clorox, Kleenex, 409, Maytag, Tappan, Amana, Oster, Sunbeam, KitchenAid, Singer, Smuckers, Planters, Rubbermaid, Pyrex, Tupperware, Dr. Pepper, Nehi, Honeywell, Levolor, American Standard, Kohler (fixtures), Crisco, Saltines, Gerber's, Q-Tips, Pringles, Lays, Lipton, Maxwell House, Folgers, Breyers, Bayer, Alka-Seltzer, Land-O-Lakes, Morton, Pillsbury, Green Giant, Smith Brothers (cough drops), Ipana, Pepsodent, Gillette Blue-Blade, Brylcreem, Vitalis, Aqua-Velva, Eskimo Pie, Butterfinger, Reese's Peanut Butter Cups.
Clothing: Stetson, Florsheim, Converse, Keds, Vans, Maidenform, Bulova, Timex, Jockey, Lee, Gore-Tex, Playtex, Russell, Sebago, Bass, Brooks Brothers, London Fog, Georgia Boot, Rayban sunglasses, Hushpuppies, Fruit of the Loom, BVD.
Sports/Hobbies/Toys: Bee (diamondback playing cards), Wilson, Rawlings, Spalding, Louisville Slugger, Ping, Taylor-Made, Lionel, Mattel, Hasbro, Milton-Bradley, Hula-Hoop, Wham-O/Frisbee, Duncan (Yo-yo), Shakespeare (fishing reels), Barbie, Polaroid, Bell & Howell (Super 8 home movie cameras/projectors), Brunswick, Daisy, Aqualung.
Eating out/Grocery stores/movie snacks: Dairy Queen, Pizza Hut, Cracker Barrel, Howard Johnson's (early franchise/roadstop favorite), Red Lobster, IHOP, A&W, Royal Castle/White Castle (two different chains with similar products), Waffle House, The Great Atlantic and Pacific Tea company (later known as A&P), Harris Teeter, Whole Foods, Jujubes, Good and Plenty, Red Hots, Junior Mints, Milk Duds, Cracker Jack.
Why?: Most have, or have had, top-notch, durable, well-made/superior goods/services in their field - generally recognized as such by those who use them. Some products were added mainly because of popularity/brand recognition. I saw no indication of whether this should be "current" or not - and "currently" many vintage items have better reputations than current similar items . . . guitars in general, vintage electronics in general, etc. Some of these I personally do not prefer, for instance: I will take a Rubbermaid product over Tupperware virtually anytime, but Tupperware had a huge impact when they started and were iconic in their own way.
Guess that's about too many by now and starting to strain my brain. Trying to only put down top/iconic brands that have not already been mentioned (difficult to read/remember every one that has been put down already, but I'm trying).
Edited for content and structure. I have tried to look up any that I was unsure whether they were American or not (Yoplait was 1/2 American so I deleted it), but I went mostly by my own beliefs here - sorry if I was wrong about that on any.