Webhosting.info publishes the list of countries ranked by the domain purchases:
Country # of domains Gain United States 22,052,967 341,433 Germany 2,262,543 59,050 United Kingdom 1,959,498 10,345 Canada 1,476,985 21,768 France 946,482 14,657 Korea 804,447 131,250 China 636,476 45,884 Japan 535,819 75,151 Spain 501,315 10,875 Italy 478,090 4,224