It's not as simple as technology
Who am I to disagree with someone of the experience of John Glenn?
Someone with no professional experience of space technology certainly.
But I do have a lot of professional experience of complex technological innovation.
That experience, if it applies to space technology, says John Glenn is wrong.
He's completely correct in pure energy terms of course. But in my experience solid infrastructure takes far more time and resources than the planners can imagine.
I haven't worked on safety critical infrastructure either. A Mars mission system has to support the entire life support, communications, navigation and propulsion for anything up to three years beyond help from Earth.
A program of testing that involves evolving similar systems for a journey to a body three days away is not just a nice thing to have, it's a necessary precursor. (Presuming that by the time Orion is heading for the moon, they have one or two craft far enough along the pipeline for a rescue launch at a moments notice. ) Even if there are launch systems the US government has kept from the world, I suspect it is very unlikely they have anything that could currently head for Mars in time to make any difference to a stricken vehicle using today's technological infrastructure.
It was technically possible to launch a mission to Mars forty years ago, maybe even further back. But technically possible does not equate to enough mobile phone masts to make a viable national network. It was probably also technically possible to build a business application system that could support all business operations in a multi-national company in a user-friendly fashion. But it would have cost more than the entire GDP of all the countries in the world to equip one large company at that time. And some of the concepts necessary had not even been thought of at the time.
Once upon a time, some of our fellow humans' ancestors crossed the vast Pacific successfully to populate new island paradises in not much more than large canoes with a sail. We have no record of how many of those "missions" were complete failures. Probably a very large number given the limited life support they could carry, the lack of navigational capabilities and propulsion by wind and oar.
But it is unlikely that any public, let alone the American public, would today accept Mars missions launched where there was say a 1 in 100 chance of the highly skilled, highly trained, probably well-rounded human beings involved coming back home alive.
FWIW I don't like agreeing with GWB on anything. But some of his advisers may have got the puppet to say this one right.
Just a pity us Brits can't show you how you're not the invincible nation you think you are by getting there first...