They don't have to repatriate it to do useful things with it. Believe it or not you can actually do interesting things outside the USA. I know right? Who knew?
Lose the snark. They already do about as much as they can with their cash outside of the US. There are a lot of reasons they keep the bulk of their operations in the US, and in Silicon Valley.
Have you wondered why Apple has taken out loans in recent years despite having gobs of cash and no actual need for the money?
No, I haven't wondered because it's blindingly obvious, and it's not the reason you state. The reason they do it is because they can borrow against overseas capital and use it to obtain cash for operations and growth in the US. It's a way of partially working around exactly the problem I described.
Over 50% of Apple's business is outside the US.
Revenues, yes. Operations, no.
The effective tax rate in the US for corporations is actually below the world average.
Only because many corporations have big writeoffs available due to depreciation, losses, etc. Apple already uses all of those to reduce their tax liability for US revenues. They'd pay full rate on money they repatriated.
I won't bother rebutting the remainder point by point, because it's all predicated on your above errors.