That is a very good observation, indded. The role of geography is clearly overlooked in the discussion of the development of modern society (except the excellent work of Jared Diamond).
But it is clear that different geographical features facilitate or inhibit different types of human interaction and thus influence the development of different types of social institution. Cold climate may indeed create the need for closer cooperation, but also is less hospitable for plantation-like agriculture, hence inhibits the growth of landed aristocracy. Segmentation (e.g. by mountains, as in Afghanistan) leads to tribalism, but also inhibits the growth of plantation-like agriculture. This issue certainly needs more careful consideration.
Wojtek