Etiquette?
It's bóllócks.
If you were to meet John Major in company you wouldn't feel the need to call him Prime Minister.
Which is why I would address Bush as Mr Bush, as you say courtesy or manners.
He's not the President so why on earth address him as such. Thankfully, for all parties, the scope for my meeting ex Presidents of the USA are limited.
I've never really understood these things, retired Military people still going by what are professional titles. It's fúcking nonsense.
Of course but, as so often, that comes purely from your own ignorance and can therefore be disregarded by the rest of us.
A former President is addressed as Mr President. Partly because the President, as Commander in Chief, effectively holds a military rank and these are observed in protocol on retirement.
You are Irish, so I suppose we can forgive your ignorance. What is this bint's defence?
Nope. THere is no comparison.
You could argue for years about whether the President is the Head of Government. The closest definitive answer is that the legislative and executive forms of government are separated in the US Constitution. What is a matter of cold, hard fact is that the President is the Head of State and the PRime Minister is most certainly not. Key differences include the fact that the legislative cannot remove a PResident but can remove a Prime Minister. The PResident's job is formally defined within the constitution and formally elected whereas the the PM is a monarch appointee, arising from a public vote to elect the legislature.
Most crucially, the PResident's job contains a formal military role and the PM's doesnt.
Most important of all, you call the ****ing bloke Mr President. If you dont like it, **** off!