I would say the characters were more caricature than imitations. To wit, Condy Rice reminded me of Roddy McDowell's partner in Planet of the Apes. The deep voice falsetto of the Colin Powell character was laughable. However, Bush Sr. was the worst of all, not even believable, even as a caricature.
Positives were Dreyfuss did a good job on Cheney, as did Brolin of Bush, and Barbara lent some comic relief, although I have not seen her as she was portrayed.
As for the content, the obvious intent was to portray Bush as the buffoon that his opponents painted him to be during his presidency, which was accomplished. As this is heading into political territory, I will leave it at that and would appreciate that others do not take the political tangent here.