As to "what does it matter if the government can't take a cut?" --- the government does take a cut, and the reason it matters is that the lower rate will, on the margin, encourage cash repatriation.
Remember too that firms know they will be taxed in the future at (unknown, but estimable) rates, and today's rate will be compared against firms' estimates of current rates.
So in terms of the government's cut I forget the numbers in the current plan but say the corporate tax rate goes from 30% to 20%, and Apple decides that 20% is As Good As It's Likely To Get, and decides therefore to bring $1B of cash into the US that at a 30% rate it would have left elsewhere -- the US gov now gets 200M, rather than the 0 it would have gotten if the tax rate had stayed where it was.
1) Apple will spend it on capital investments (factories, campuses, data centers, etc.) in its business. Doesn't benefit the government, but benefits the country.
2) Apple will spend it on R&D / employees. Doesn't benefit the government directly, but benefits the country.
3) Apple will dump it into an American bank. That bank has a reserve ratio that is relatively low. It will lend several times the amount that Apple deposits to people or corporations who will do 1) or 2)
4) Apple will spend it on buybacks and dividends, which ultimately ends up in the hands of Apple's owners (you and me through our 401(k)'s, and probably a bunch of rich people as well), who will do 1), 2), or 3)
So, whether or not the government gets a cut, it benefits everyone who actually lives here.
The repatriation is just a tax/accounting fiction. Yes, Apple now has more flexibility to do with that cash what it wants (mostly return capital to shareholders through dividends and buybacks), but on aggregate for the economy it doesn't make a huge difference.
[1] http://investor.apple.com/secfiling.cfm?filingid=1628280-16-...