Two points,
1) several countries have multiple gauge national systems (India and Australia come to mind). If the Grand Narrow Gauge Trunk had been successful, the US might have been included.
2) We have been very fortunate with Colorado (others come to mind also) having many period photos of narrow gauges. The Gainesville, Jefferson and Southern does not have one (about 50 miles long), the Gainesville Midland had three (all of the last narrow gauge train in Georgia at different stations), and the Roswell Railroad (10 miles) has only one.
Doug vV