From what I understand, it is illegal as per the USDA to bring back pimento wood into the US. It could be environmentally hazardous if something was in the wood like bugs you may not even see. Its no different than bringing meat or fruit. Not sure about the treated mentioned.

For use in a smoker I 'd recommend applewood chips which are easy to find in the US and throw some pimento berrys on the wood for flavor.

There are websites that sell pimento online. I 'd suggest obtaining it that way.