Seems that Friedman would prefer to address the "perfect world"--in which case, of course, his theory would be correct.
By ignoring the reality--that is, that certain Governments manipulate the system for their own advantage--Friedman simply demolishes his own argument.
Au contraire ... Friedman demolishes the argument that Government can even attempt to "manipulate the system for their own advantage". Any such attempt is self-defeating. Tariffs harm your own economy, so if other countries had high tariffs, they are the ones suffering for it; it would be folly for US to follow suit.
On the other hand the best of all worlds is reciprocal free trade, which is what USA is approximating in trade deals like CAFTA and NAFTA.