When I said that I had "never heard of it North of the Gulf states" I was refering to Chaga's disease and not not the assassin's themselves
As for assassin's being beetles, that isn't quite accurate. They are actually part of the insect clade known as 'true bug' and are more closely related to thing like bed bugs and cockroaches
You asked about size. Most of the ones you will see inside the States are onlu about 0.5-.75" of an inch although there is a species, know as the wheel bug, that can reach upward of 1.5" Some species in S. America can break the 3" mark.