Nuclear weapons have proliferated to nine nations around the world since the passage of that act. The production of nuclear armaments is clearly limited by political will and industrial power, not knowledge.
The act protects a foreign policy establishment that has abused its power to conduct dirty tricks against other nations for decades in order to keep American elites rich and in power.
No one is going to invade the American homeland, given the vast oceans separating us from the rest of the world. Repealing that act and removing the foreign policy establishment from power would unwind our vast empire abroad and greatly improve our relations with other nations.
I would prefer that we do this cleanly, but unfortunately I think our empire will suffer a far messier fall from power over the coming decades. Empires at this stage flail wildly in their military adventures.