I have one question to Cryptic. Why are these contest restricted to X country only? Is the problem somekind of legal hassle or what?
If that is the problem then I'm afraid that these contest will happen in "big" countries only and I don't happen to live in such.
Legal reasons are almost always the reason that contests are limited to certain geographic areas. Different countries have vastly different rules concerning contests ranging from eligibiilty, tax reporting, notification, participation, etc. That is why most companies won't sponsor international contests. It is too expensive to guarantee compliance everywhere and often impossible.
Slightly off-topic question (apologies), but: Are North American competitions generally inclusive of Canada too? Or is that considered too different to allow it?
I'm not an expert, but it depends on the contest. Canada and its provinces have different rules that the various states in the U.S.
Most contests run in the U.S. aren't applicable to all 50 states for the same reason that most contests exclude other countries. The laws relating to contests in the United States aren't solely impacted by federal law. The various states have their own laws concerning eligibility, participation, notification, distribution of prizes, determination of winners, etc. That is why you might hear something like "contest not valid in Maryland, Tennessee, and New Mexico" (to pull three random states out of thin air.