McGrath, as usual, is correct about the importance of the service being free at the point of delivery. However, the general argument here misses a very important point.
All the major social reforms of the last century or so, from the 40-hour week, paid holidays, free education, sick pay, old age pensions, equal pay for women, abolition of child labour and so on occurred not because those in power were persuaded by logic or morality. They occurred because they were perceived to be necessary in order to stave off revolution by a politicised, organised, class-conscious workforce.
Most of them were first conceded at a time when there still appeared to be an alternative way of organising industrial societies besides US/Western European style capitalism. In order to maintain the legitimacy of liberal-democratic capitalism, reforms like the NHS were conceded as a result of working-class struggle by a ruling class that saw conceding such reforms as a preferable alternative to the revolution they feared.
Now that no-one is talking about an alternative to capitalism the ruling class has no incentive to make any concessions for the simple reason that the bastards aren't scared anymore.
There is no mass, effective class-based political movement in the United States and so there will be no significant reform of the healthcare system.
And we'd better watch it in the UK as well.