Mac-n-cheese is pretty common all over the US. My parents both came
from Texas & were raised on homemade versions. I was raised in the
Midwest, and we had it often for lunch or dinner -- either the
made-from-scratch version or that made from a box (Kraft). The nice
thing about it is that it is pretty versatile. It can be made of
almost any sort of pasta: Noodles, macaroni, fusilli, etc.; you can use
almost any type of cheese or combinations thereof; you can add almost
anything to it in the way of spices to jazz it up; you can add more or
less milk, sour cream, etc. to change consistency Our favorite growing
up was the standard "Mac & cheese with tuna" -- made with canned tuna,
peas, and cream of mushroom or celery soup. A friend at a former job
also introduced me to tomato mac-n-cheese: Dump a can of either Ro-tel
or plain tomatoes into the finished product. By changing the cheeses,
the pasta, adding things such as garlic or onion, and using a topping,
it can be served at an elegant dinner party. It also is a favorite
with fish, chicken fingers, and any variety of other meats. It is
inexpensive, easy to prepare, and makes a relatively quick side or main
dish.

I think that its versatility & ease of cooking have helped win it
acclamation as a "comfort food".

~Eri in Texas