magnitude greater than Iraq / Afgh put together.

And if we're also taking policy into account, how can we pass over Carter?

Of course the Iraq war royally screwed the balance of power in the ME, and backfooted US reputation, but it's hard to know where an alternate history without the invasion leads. The ME was a mess long before OIF with input from any number of influences.

We've had some poor leaders, but Trump is laying the groundwork for disaster that could take quite a while to fix. Everyone is simply hoping (despite all evidence) that Trump doesn't precipitate economic calamity through protectionism. Meanwhile he's debasing politics, pouring gasoline on already worsening partisanship, and constantly attacking institutions of government. Trump isn't the only one to blame for some of that, but he's augmenting it. A bit of the chicken / egg debate.

I think he'll end up in the discussion for worst before his tenure is out.

Like others in this thread, I'd also welcome GWB back in comparison (preferably sans Cheney).