Weakest version of Earth that could survive the alien invasion from Tatsuki Fujimoto 17–26? (opens in new tab)

What is the weakest version of Earth that could survive the alien invasion from Tatsuki Fujimoto 17–26 Episode 1? No space-age civilizations are allowed. Earth must rely only on what exists on the planet. "Space-age" means no off-world colonies (Mars or beyond), but advanced or future...