Well, the bugs have to contract the disease from somewhere before they can pass it on to humans.
Modern building techniques, modern plumbing, and modern waste removal have mitigated most of the breeding grounds for the disease here in the USA. I would guess (with no factual support what so ever) that most of the cases being seen are from recent entrants to our country from areas where the disease is more common.
One of the disease vectors for Chaga’s in TX is possums. The anal sacs of the varmints is a reservoir for it
The primary wildlife reservoirs for Trypanosoma cruzi in the United States include opossums, raccoons, armadillos, squirrels, woodrats, and mice. Opossums are particularly important as reservoirs, because the parasite can complete its life cycle in the anal glands of this animal without having to re-enter the insect vector. Recorded prevalence of the disease in opossums in the U.S. ranges from 8.3% to 37.5%.
Studies on raccoons in the Southeast have yielded infection rates ranging from 47% to as low as 15.5%. Armadillo prevalence studies have been described in Louisiana, and range from a low of 1.1% to 28.8%. Additionally, small rodents, including squirrels, mice, and rats, are important in the sylvatic transmission cycle because of their importance as bloodmeal sources for the insect vectors. A Texas study revealed 17.3% percent T. cruzi prevalence in 75 specimens representing four separate small rodent species.