My entire post was a response to "flat tax is impossible to avoid", and has nothing to do with rates.
I agree with you that if the US tax rate was more in line with other countries, it would remove the incentive to offshore profit.
In the mean time, all the tax revenue from economic activity that couldn't be offshored anyway is also being reduced. So while you get your 15% of $100 billion you are also reducing from 35% to 15% of the revenue you were getting from everything else.
Also, such a move can trigger a race to bottom. For example if we switched to 15%, Ireland, missing all that tax revenue, figures 10% of $100 billion is also better than nothing. So they switch to 10%. Then Switzerland decides 5% of $100 billion is better than nothing, so they lower it to 5%. Then the Republic of Sealand figures 0.2% is better than nothing...
Apple has about 50 billion onshore and around 100 billion offshore. If you're getting 35% of 50 billion that's 17.5 billion in total taxes. If you get 15% of 150 billion that's 22.5 billion in total taxes. 5 billion more tax dollars seems like a better deal, but that's just me. Not to mention all the extra jobs and spending that would be created. As far as your theory of a world competition for lower tax rates if the U.S. lowers it's corporate tax rate, well again it's a theory. If it did come to pass I say great. Less taxes means less government spying and less killing innocent people all over the world. That's a good thing.