The Americas Zone was one of three zones of competition in the 1978 Davis Cup. As in previous years, entries from South America were to be placed in one half of the draw, while entries from North and Central America, along with South Africa, were to be placed in the other. However, Canada, Mexico, Venezuela, and the Caribbean/West Indies withdrew a week before the draw, in protest over South Africa's participation.
The South Africa / United States tie, at Vanderbilt University in Nashville, became a focal point for the international opposition to South Africa's apartheid policies. In an effort to appease its critics, South Africa named Peter Lamb as one of the six members of its team, as its first-ever "coloured" player. However, Lamb did not play, and his inclusion in the squad was derided as tokenism. Crowds of up to 5000 turned out in protest.
South African regular Ray Moore withdrew from the team, saying "I am a South African and I intend to remain one. I neither embrace nor endorse the policy of apartheid. I do resent the interference of politics in the Davis Cup. In particular I wish to play no part in a situation which threatens to turn a sporting event ... into a political demonstration." After a decade of dispute, South Africa would be excluded from the 1979 competition, and would not be allowed to compete again until 1992.