Conflicting Cultures In Two Future Histories

The Night Face, II.

In Poul Anderson's Psychotechnic History:

Solarians

Nomads

Erulani

Alori 

- see The Peregrine II

- and also:

Stellamont

- see Conflicting Cultures

In Anderson's Technic History, Namericans are enthusiastically welcoming and sociable whereas Lochlanna are elaborately and guardedly courteous and Gwydiona are both friendly and hospitable but in an unusual, almost alien, way that extraplanetary visitors must try to fathom.

Cross-cultural contacts across space and time are one theme of sf, e.g., the Time Traveler and the Eloi.