Does the Quran say somewhere that Allah has confused the minds of the infidels? I'm sure I read something like this before, but can't find the actual reference.
Do you mean misguidance?
... So when they turned away (from the Path of Allah), Allah turned their hearts away (from the Right Path). And Allah guides not the people who are Fasiqun (the rebellious, the disobedient to Allah). [Qur'an 61:5]
Verily, those who disbelieve, it is the same to them whether you warn them or do not warn them, they will not believe.
Allah has set a seal on their hearts and on their hearing, (i.e they are closed from accepting Allah's Guidance), and on their eyes there is a covering. Theirs will be a great torment. [Qur'an 2:6-7]
Allah mocks at them and gives them increase in their wrong-doing to wander blindly.
These are they who have purchased error for guidance, so their commerce was profitless. And they were not guided.
Their likeness is as the likeness of one who kindled a fire; then, when it lighted all around him, Allah took away their light and left them in darkness. (So) they could not see. [Qur'an 2:15-17]