The economic angle also doesn't make any sense for Bush politically because of his donor base.  Investment banks and insurance companies are his big donors.  And most, if not all, of them have large operations in London.  That's to say nothing of the damage that would be done to American shareholders -- whether wealthy individuals or pensioners or whatever other group -- because of the resulting losses in profit, and at a time when people were being hit quite hard already.

Be nice to America. Or we'll bring democracy to your country.