I'm contemplating what you wrote and have come to the same question. Is this not exactly what Israel was doing? They built extreme defensive measures (Anti-tunneling Wall, Iron Dome, Security Checkpoints, and DMZs). And trained their military every single day. That sounds A LOT like the porcupine defense you advocated. Then when the attack did come, they've done all they can to make their attacker suffer mightily.
Non-interventionism? So we can have no allies in the world? Or we won't support them if they need it? Should we stop world trade? Isn't that economic interventionism? Should we end all immigration? That would end cultural interventionism. And how far back do we undo interventionism that has already occurred? Do we all return to Europe and Africa and return the entire Western Hemisphere to Native tribes? Give all of the Middle East to Turkey to rule and restore the Ottoman Empire? Does Ukraine go back to Russia?
But regardless of Israel or interventionism, you still skipped my questions. You avoided all of my questions and instead gave an unserious answer "Be like a porcupine". That's the kind of answer that leaves me with 1 of 2 conclusions: You are either terribly naive about the real world, or you are just a farce and completely unserious about any of these topics. I'll let you tell me which it is.