ALCO had the US license to produce the Garratts. Reportedly the builder was never successful in getting CMO's to experiment with the British design because (1) it was too "foreign" and, (2) fears that as coal and water over engine units was depleted, weight on the drivers would be diminished negatively impacting adhesion and tractive effort. Managers don't like to stick their necks out recommending that their bosses buy unorthodox technology just in case the higher ups later have to ask, "What idiot recommended this piece of junk?"
Back in the 1980's I witnessed the big Garratts climbing over Montagu Pass and elsewhere in the Eastern Cape of South Africa. They were really, really impressive so see. The "little guys" on the SAR 2 ft lines were impressive in a different way. They represented the absolute apex of steam technology for a gauge that narrow.
Fortunately, there are a few ex-SAR 2-foot Garratts still serving on the Welsh Highland Railway, along with the very first Garratt ever built (for Tasmania). The WHR has impressive scenery, impressive motive power and beautiful passenger equipment. You owe it to yourself to see this line before you check in at the "great roundhouse in the sky." It's well worth the trip to the U.K.