Geographic determinism is one of those theories that explains everything after the fact and predicts almost nothing
You could say that about any other determinism. Nevertheless, it's a huge factor in the wealth of nations and a pillar of geopolitics. It's also why we don't all speak german today... /s
Most of this isn't geographical determinism, though. The death of the indigenous americans (allowing settlers to come in and take over), the brain drain after WW2, the first modern democracy (even if the Constitution is a bit kludgy), etc., all not geographical determinism.