I don't think that's quite fair. It's true that after the arrival of the US, Japan was apparently fed up and changed its approach. But does that make invading and subjugating their neighbours justifiable?
Sort of. If you feel there's a greater power out there that's building up to invade you and your neighbours, forced unity can seem like the lesser of two evils. The US was not super friendly in the first half of the century, Hawaii and the Philippines were both recent military conquest dangerously close to Japan.