There are a couple of important differences between 'old world' resins and US made resins. First, we have stringent EPA regulations (although not as strict as Canada's) so there are many chemicals that we cannot use in this country. That is particularly true of dyes, which is why all of Fender's pretty Stratocaster guitars are made in Mexico. Second, our OSHA regulations make using certain chemicals prohibitively expensive due to the safe handling requirements. Lastly, the economic value of making resins with the US's hourly wage rates makes it even less attractive when doing heavily detailed and customized work. I'm sure there are other reasons as well.