I would guess that the explosion of sites in the U.S. in the earliest stages of the WWW probably outpaced setting up rules, here. (I have heard of movements to bring “everyone” into some sort or world-wide compliance, but I don’t know where those efforts have gone so far.)
OTOH, have you found every foreign site to have a country domain node? Or only those from universities? I have noticed that a lot of U.S. schools are tagging .us onto their sites and pages.
For those who are interested, here are some sites that list the possible domains by geopolitical region. The ISO3166 list is the common international list for post offices, EDI transfers, etc. outside the WWW and/but the WWW has (with one big exception) adopted the ISO3166 2-letter codes.
(The ISO3166 folks looked at the United Kingdom of Great Britain and Northern Ireland and assigned a code of GB. The WWW folks looked at the United Kingdom of Great Britain and Northern Ireland and assigned the code .uk.
The sites are
http://info.ripe.net/ (home page of RIPE: sets and maintains the ISO3166 codes)
http://www.centr.org/tld.html (RIPE’s list of domain codes with hyperlink contacts for more info)
http://www.indigo.ie/egt/standards/iso3166-en.html (A list of all the ISO3166 codes)
http://fotw.digibel.be/flags/iso3166.html (A bit off-topic, but related to the ISO3166 stuff: a site that displays each nations flag, with a description of the symbols on each flag, organized by ISO3166 code)