Pete,  I don't want to be argumentative but John is absolutely correct.  You are correct in saying that not all calls come from out of this country.  However,  whether the calls are coming from within or without of the country,  the DNC was never created to deal with scofflaws.   At the time of creation,  the scammers and illegal telemarketers were not yet an issue.   The only reason the DNC was created was for the sole purpose of limiting the number of Telephone marketing calls (Telemarketing)    from legitimate and Registered with the FTC Businesses  to those citizens who registered with the FTC not to be called.  And it has worked very well.  I regret that there any exemptions at all.   Only those businesses who are Registered within the FTC data base are required to purchase the DNC list.    To purchase the list they must register their business with the FTC,  principals,  sic number,  FEIN tax number,  phone numbers,  physical and mailing address, must maintain their DNC file of in accordance with the FTC,   for their examination upon request and observe all the laws and proprieties of the FTC/DNC.    They purchase,  maintain and honor this list because most legitimate American businesses  do not wish to offend those who are on the list.  Probably 99 percent of all unwanted callers come from those who are scofflaws or do not come under the DNC.   Most of the complaints filed with the DNC do not qualify as legitimate complaints because so many report everything to the DNC instead of the appropriate government agency.  Any complaint that does not comply with the DNC's purpose,  such as a complaint of an unwanted caller....unknown,   scammers,   or a complaint filed against a business that is not registered within the FTC data base,   is either passed on to the appropriate agency or goes to file 13.   Sometimes when people file a complaint they will receive a return computer generated message from the DNC advising them that the subject of their complaint is not registered with the FTC.  And they don't know what it means.
I am sorry that I have labored on for so long and I hope I have not offended anyone.  Most people simply have never read about the DNC or been to their site and get their information from others who have never gone to the site.    The simple matter is that the DNC is working as intended.  We do not get calls from Those legitimate,  FTC Registered American businesses who purchase and follow the rules.   They are too easily found when violation occur.   10K-16K per violation keeps the would-be  guilty....honest.