What dystopian future described in book or film have we come closest to, or seem on track to become?

An inconvenient truth..

Idiocracy! Definitely, Idiocracy! – except it is happening now, not hundreds of years in the future.
Watch the opening scene

And the president’s State of the Union speech
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@LuckyGuy Idiocracy is a wonderful movie!

About 20-some years ago, I read The Handmaid’s Tale. It was incredibly disturbing. Today, it is even more so with the direction that the US is moving.

I thought of this question while watching V For Vendetta. We aren’t far from that.
Contagion is obviously close to our situation, but it isn’t quite dystopian.