Final answer:
The folk culture is an example of a subculture that has all but disappeared in the United States, primarily due to technological advances and cultural globalization.
Step-by-step explanation:
An example of a subculture that has "all but disappeared" in the U.S. is the folk culture. Folk culture typically includes people who live with few modern conveniences, follow age-old customs, and have an economy that is less reliant on cash and occupational specialization. A distinct example of this in the United States could have been the communal societies of the 19th century or certain Native American groups that have since been assimilated or have declined significantly in members practicing traditional ways of life. By the mid-19th century, the spread of technologies like the telegraph and the railroad, along with cultural globalization, led to a decline in folk cultures which thrive on isolation and are defined by local, non-commercial practices. As these communities integrated or vanished, their unique practices often became part of the broader American popular culture or ceased to exist.