They are definitely NOT a southern thing. There are American cockroaches in northern Minnesota. First step is knowing what attracts them, and it is NOT being filthy. Short story that led to my education on the subject. Every late spring we have a HUGE moth and gnat problem. So, I took a high velocity fan, attached a screen bag to the output side and put a light in front of the input and set it on the deck. I was sucking up bugs dozens a second. Every moth within a quarter mile met its maker. However, moths were not the only thing in that bag, as I came to realize sitting there watching it one night. A roach landed right by the light and, with all its traction and speed, evaded the suction. There were about a dozen in the bag.
It tuns out, male cockroaches take flight in late May through June in search of a mate and they ARE attracted to artificial light. Them being allegedly afraid of light and not in the north, uneducated myths! Keep your exterior lights off and curtains closed during these months, because if they do wander in and happen to find a food source, you are thoroughly screwed (almost).
Luckily, they didn't make our place their home, but I can tell you what kills them. Permethrin. It is a common ingredient in Home Defence (although I buy it as concentrate for mosquitos - a Hy-Yield product called Super 38). Apply it around the exterior of your home and near any entrance points like eve vents etc. Keep your recyclables and trash away from the house and vacuum/take trash out regularly. If you meet the threat head on knowing how they operate, you will never need to worry.