To me, it's much more constructive to visualize what a huge amount of money can buy, not the money itself. (One of the other commenters is right that it only makes sense to divide a trillion dollar debt over 300 million people. But I think numbers in the millions or even a billion should be visual because projects of this size are
local, and so are not split over every American.)
$1 million is roughly how much a median-wage American ($40k/yr) can save by living modestly above subsistence levels ($18k/yr) over a 45 year career. I call it "a life's work".
Now, this isn't just a hobby or side project. Most people happily and rightfully include raising their children as their proudest life's accomplishment. It's "what can one do in a human lifetime after paying for room and board".
Anyways, this helps me think harder when our local government wants to spend $5 million on a project. Is it really worth 5 life's works? Maybe, maybe not.