Probably
Speaking as a Unitedstatesofamericanian, I can tell you it's not even a controversial question any more in the US. People just accept that he is. It's certainly true that has succeeded in alienating every corner of the US political spectrum. The conservatives hate him. The moderates hate him. The liberals hate him. Etc.
In terms of foreign policy, he has the eerie, and frightening knack, for always choosing the wrong course of action, in every instance. Even Nixon could point to his breakthrough in China to offset his failings. I fear Bush will have an entirely negative legacy.
As to whether, from a historical perspective, Bush is "the worst" is an interesting question. I'm inclined to give that honor to President Wilson. Not an obvious choice, I know, but:
(a) He got the US involved in WWI, which was a war we absolutely had no reason to be in.
(b) Acquiesced to the Treaty of Versailles, whose provisions led to WWII.
I know it depends on how far you want to stretch the chain of causality, but one of history's big "what ifs" is what if Germany had won WWI? There would probably have been no WWII, no Holocaust. And a German victory would have been far more likely if the US had not intervened on the side of the Allies.
But yeah, Bush is an incompetent ****. No question.