Someone remarked, qutie a while ago, in a conversation: Americans have trust in God, Britons in the NHS. If godliness of US society cannot and should not be underestimated, nor can the attachment of vast majority of Britons to the NHS.
The NHS binds the British society together, and a manifestation of the welfare contract between the people and the state. The attitude towards the NHS is one of the few things in Britain that transcends class, and it was set up just after the Second World War when the Empire was ebbing and the state finances approached near bankruptcy. No system is perfect: there are wrong decisions made (usually by administrators rather than the clinicians) and waste. Many Britons have horror stories to tell in glee, despair or anger, yet they believe in the principles of the NHS.
So Americans be aware: attacking the NHS as a symbol of failure will be seen as a personal attack by many Britons.