Mature Americans are still found in a few places where blight did not get to, and they are called ‘escapes’. A rather large 60 acre plot of them was still blight free a few decades ago, but has since been infected. I’ve seen many as tall as 70 feet in remote locations, but it is true… blight is endemic and escapes are living on borrowed time. Some uninfected populations exist outside the USA, too.
There are breeding programs underway at the American Chestnut Foundation and the American Chestnut Cooperative that seek to get blight resistance from Asian sources into trees that have American form (very large). There are also genetic engineering projects underway, and blight is not the only pathogen/pest American chestnuts face. There is phytopthera and the chestnut gall wasp, both imported.
There are also projects involving weakening the blight fungus (hypovirulence).
Because of huge advances in biotech in the last decade, I think the blight issue will eventually be overcome. Climate change and other factors of course threaten the entire environment, so who knows what challenges will arise next. There are many threats moving around the globe daily thanks to globalization short circuiting billions of years of evolution.
Meanwhile, Asian chestnuts with blight resistance can thrive in orchards, but not forest settings. We won’t run out of chestnuts, but it will be a while before we see Americans back in the woods in any meaningful way.
It was a huge hit to the American forests when blight ran through them. Majestic trees. Amazingly large and dominant in the forests of old.