I am quite the Godzilla and kaiju eiga fan, so I will answer your question as best I can. To start off with, the exposure the west had to Godzilla and that genre was seen through the lens of a pro-nuclear nation, one that thought to control nuclear power instead of giving it respectful space. The Japanese experience was very, very different, and their interpretation would rightfully be different. No country other than Japan has had nuclear weapons used against them, let alone twice. Godzilla is often seen over here as a symbol for atom atomic power, which is not correct. The original Japanese creators of Gojira(Tanaka and Honda) were rightfully influenced by the events that had taken place around them in the 9 years since Hiroshima and Nagasaki. The Daigo Fukuru Maru incident also helped to create the nuclear monster age in Japan. Within Gojira, there is a scene where a woman remarks about how the discovery of Godzilla is affecting the fishing, a direct reference to the Daigo Fukuru Maru accident.

Gojira is not simply a commentary on nuclear power, but nuclear testing and the horrors it unleashes. Dr Yamane remarks-after Godzilla was silenced by Serizawa- that there may well be others created by the horrors of mankind.

Toho’s Godzilla series we’re not the only genre to explore these nuclear questions. Deiei’s Gamera, while originally a cheap riff, was elevated to a new status during the 90’s Gamera Trilogy, posing large questions not just about nuclear power, but of human’s role in the environment and world at large.

A more layered metaphor can be found in Neon Genesis Evangelion, a series known for its deep metaphor and analyzation. The use of N2 mines to destroy the angels are a possible symbolization of the jadedness with which modern society has treated nuclear weapons. The citizens are not surprised when one is detonated in the ongoing struggle for the preservation of the human race. Also in this way the angels can be seen as judges of human action, greed, and overstepping it’s limitations, just like Gojira.

It is no surprise then that Hideaki Anno( Evangelion) directed Shin Godzilla, a spiritual reimagining of the original. In the film, as a new life form slowly evolves, emerges and destroys Japan( Godzilla), the Japanese government and ministry are powerless to stop him, as they continue to be caught up in protocol and procedure. This is a open critique of the Fukushima accident a few years prior, illuminating the slow response that the Japanese government had in addressing both the earthquake and nuclear questions.

To circle back to your original question, the Japanese response was actually rather unified. Many Japanese felt represented through these works, their experience shown outside of their home country. One theater showing Gojira reported audiences crying, and actually running from the theater, as the same theater was attacked in the film.

The reduction in the themes and messages comes from the western distribution of these works. As mentioned prior, the west reduced Gojira to another atomic monster movie, inserting new scenes with Raymond Burr, dubbing over the existing track, and cutting some scenes. The powerful nuclear message was lost.