Phil could've simply taken an unplayable, wherever his ball ended up. He could've gone back to within a club-length of where he putted, probably gotten out of that hole with a 9 or a 10 at-worst doing so.
It wasn't about speeding up play. They were in position. The guys up ahead were struggling with the conditions just like they were. Even had he decided to not declare the ball unplayable and played it from where it would've ended up - they still wouldn't have been put on the clock. So the slow-play thing just doesn't jive.
He wanted to make a statement. And he did. And I think he'll regret his actions looking back on it.
Phil has a very narrow window of opportunity to achieve the career grand slam. In his mind he probably thinks the USGA and their trickery has it out for him, that they don't want him to win their tournament. If he's that upset with the organization - simply don't play. And honestly - I wouldn't blame him if he decided to not play any more US Opens. I think boycotting the event would be a much better statement than him making an ass out of himself as he's trying to make an ass out of the USGA.
I'm sure he was frustrated, but he would be the last person I would expect to protest the setup in such a way.
He had options. He just lost it, and then tried to act like he was smarter than everyone else when he was called out for it.
And it backfired.