Citizens of the USA make up 44 % of the members of chess.com whereas the country in second place contribute only 5.7 %. Why is there such a huge difference? Is chess really so much more popular in the US than in other countries? Or do people elsewhere prefer other sites?

Well, chess.com was made in USA..so, I guess more people know about it there..

The United States is the third most populous country--after China and India. Maybe one of these days chess.com users from China and India will outnumber Americans.

It is interesting to note that members from the UK are placed at the 6th place, but if one were to include the figures for all its constituent regions that are listed separately (Great Britain, England, Scotland, Wales, N. Ireland) they would actually form the second largest group.

Secondly, I wonder why there are so many in the International category. Is there any specific reason why they prefer not to choose a country? Just curious.

Are there other chess site which use other primary languages? I imagine, for one,  Russia would have one

Interesting. Do most of the population in Russia have reliable access to the internet, for example in the larger cities?

I'm interested in the "numbers" you provided, Horned_Owl, where did you get them?

MEMBERS -> Country List.

Great Britain and United Kingdom have traditionally been great rivals.

Country	Members	Percent	Avg. Rating	Top Rated
United States	1062215	45.69%	1291	Gonnosuke (2911)
International	143506	6.17%	1369	JbRiver1 (2711)
India	115129	4.95%	1347	XanatosGambit (2573)
Canada	97339	4.19%	1306	Jeff18 (2724)
Great Britain	95437	4.1%	1242	MarcellinusDelsink (2725)
United Kingdom	79942	3.44%	1343	sproates (2861)

Interesting? Do most of the population in Australia have reliable access to the internet, for example in the larger cities?

It's not restricted to the larger cities ...

http://www.youtube.com/watch?v=RWZEkRaPGcw