Try a bill nationalizing banks or insurance companies and see how far we get with the present constitution, the ruling about AAA running in this sense. Not exactly sure how we can therefore term this document giving "enough leeway to do just about anything..."
And try amending the thing. With 50 states and fractional, regionalized power bases, it's pretty hard to imagine the thing significantly amended. This is of course assuming you can get 2/3 majorities in Congress, itself no small feat.
It's great for property rights. Which is a good thing, assuming you've a fair bit of it. Fai de bèn a Bertrand, te lou rendra en cagant
As far as nationalizing things, I'm not sure it couldn't get very far. States regularly have taken over power utilities for instance with nary a whisper. I.e. I don't think the constitution would outright ban it if there was a good reason to do it.
As for amending being difficult, I consider that a good thing: the crazies who periodically have power (e.g. religious right) can't permanently enshrine horribly bad things in the constitution.
But here, you run into problems of scale (esp. acute in things like the Great Depression). And in any event, if having a third of Americans malnourished, poorly housed and clothed were not such an event as you describe, then I'd argue that there are no such events. Fai de bèn a Bertrand, te lou rendra en cagant
