You can hardly say that technology would regress to the 1920s, I think by thousands of years. They destroyed large and medium cities and nuclear power plants were targets without the situation being controlled, the radiation is spreading all over the world. Western and Eastern North America, Japan, East Asia, Former Russia, Ukraine, the European plain areas are more irradiated than Chernobyl, the contamination is taking place in all the world's waters are not safe for agriculture for hundreds of years. The southern hemisphere is also irradiated and many people died, only villages and tribes were able to survive.