@lorrie48 I really love answering this question.
First, Lady Windermere's Syndrome seems like somewhat of an outdated theory to me now, as we learn more about Bronchiectasis and are discovering more of it around the world. My theory is, these tended to be older, somewhat wealthy patients with access to the best (in their time) health care. Add to that genteel, doing what ladies did - taking care of indoor and outdoor plants, often in humid greenhouses of conservatories.

Much of the rest of the world just lived with it, probably quite often no medical care. Before x-rays, its existence was a mere guess. Even with x-rays, what was causing the lung problem was not always clear. It was the development and lately, the availability of the CT scan that really accelerated the diagnosis. So probably Bronchiectasis was always there, but nobody knew how widespread it might be, until probably the last 10-15 years.

Now the theories of cause include not only the genetics previously believed, but chronic asthma, repeated bronchial infections or pneumonia, and exposure to harmful chemicals or bad air quality.

As far as NMT/MAC are concerned, the bacteria are everywhere. So, if you are predisposed to it, by virtue of having Bronchiectasis, COPD or Cystic Fibrosis, you can catch it anywhere. Perhaps in some area, due to soil content and how mobile the soil is, or concentration in certain water sources, it's probably more prevalent. Other known sources of concentrated NTM are hot, humid places like indoor hot tubs (and possibly steam rooms or hot yoga rooms?), swamps and and hot water tanks that are not kept at a sufficient temperature to kill the bacteria.

Mine infection likely came either from years of gardening, or from direct exposure to heavily contaminated soil (where feral chickens lived) or hiking in desert dust in the Southwest.

If you are really curious about the dispersion of NTM/MAC or where areas of more bronchiectasis are being identified, try searching using scholar.google.com. There is a lot of new research going on. I compare it to when Black Lung was identified in coal miners, or Asbestosis in vermiculite miners and insulation workers - many more cases are found when the doctors know what to look for.

Do you have a pulmonologist who is specifically familiar with NTM?