The Ming are still in power, I think the Chinese would be able to slap down any direct attack by would-be conquistadores.
Which is why I think this is particularly interesting - instead of the OTL relations between arrogant, introverted Chinese governments and greedy trade-obsessed Europeans culminating in the Opium Wars, we'd have an early direct confrontation between two of the greatest empires in the world: the Spanish, with what at this stage is the best army and the largest navy in Europe, and the Ming Chinese, at a time when I believe the Zheng He-era fleet still existed, albeit in a decayed state.