Peruvian
The proper adjectives are:KoreanPolishAlaskanBelgianSwedishFrenchRussianCubanPeruvianIndian
Large and varied are both adjectives. South would be an adjective if it were not part of a proper noun. Amazon is likely a noun adjunct here, but Amazonian would be a proper adjective.
The proper adjective for southwest is "southwestern."
The proper adjective is Haitian.
The proper adjective for Portuguese is "Portuguese."
Cuban and Peruvian are the proper adjectives for Cuba and Peru.
Vietnamese is the proper adjective for Vietnam.
The proper adjective for Georgia is Georgian.
The proper adjective for George is Georgian.
Freudian is the proper adjective for Freud.
Mayan is itself a proper adjective.
The proper adjective for Siam is Siamese.