I don't think its just the US that is not represented well on the forum as it will be the same with all countries. I know several big collectors in the UK who are not even online and several who would not even contemplate joining a forum. Similarly I know several LAH collectors in Europe that I have met from this shared interest and, in my travels meeting German veterans many, who have bought toy soldiers because of their service and, they are not interested in shows or forums etc but, I would venture have as big or similar as heavy participants on here. I know one collector in my village who has over 15,000 TS covering about 50 years.
Its similar to how long is a piece of string this forum will be in some way a reasonable demographic of the collectors worldwide and in some ways not. what are you basing your sample criteria on? Any sample controlled etc would hold a bias and, as with most research projects a slant is gained from the researcher and, the original hypothesis.
Andy just recently mentioned the size of the collector numbers as some 30,000 If I remember rightly so, this forum has some 3,000 members of which only a small number are active but, again, that tells us nothing really and, are points.
Mitch