How has Bush failed the US?

That is not at all clear.

The “commanders on the ground” do not make the decision to send more troops, as Bush said - that’s the job of a Decider Guy.
Oddly enough, as that link shows, Perino’s “clarification” was

Bolding added 2 places for comparison.

If we’re going to count stuff he couldn’t get passed then I would say that he failed our country when he tried to privitize social security by lying to us and telling us that it would solve the social security liquidity crisis (when in fact it would only make it worse).

On the plus side, he has been spending money in Africa on worthy causes to buy some international goodwill.