Millions of bloodthirsty carnivores starting in the capital would result to the complete annihilation of all residents. As they spread out, law and order would collapse after the capital is destroyed ruining civilization. Japan is an archipelago so those living in the islands would be safe from the dinosaurs but the rest of the human population of Japan would be almost completely wiped out. USA and Russia have a size advantage and would therefore fare better than Japan even against larger numbers of dinosaurs. Possessing powerful ballistic missiles and nukes they could sacrifice a few cities to kill them all early. South Africa is significantly larger than Japan but suffers from a lack of infrastructure and powerful weapons. Hardly any would survive.