Without the courts (paid for by taxes)
You've never been involved in a civil case have you? The participants in the case pay court (or arbitration) costs, its not some service you get for free paid for with tax dollars. This ignores other costs or accessibility issues.
As far as national defense is concerned, this will likely not be paid for on a voluntarily basis.
Because people cant defend themselves? The worlds most powerful military couldnt conquer a nation of goat herders, in a area smaller than Texas, with a population only 8-9% of the US's and a fraction of the number of arms in private hands.
b-b-but muh roads!
Private companies build them, not the government.