It seems like most people who gave it 1 star had their patriotic sensibilities offended. While it definitely poked fun at the US, it was still a funny and entertaining movie.
It had a cool cast like Channing Tatum, Andy Sandberg, Simon Pegg, Will Forte, and Killer Mike. The voice acting and 2D animation were cool. The animation was similar to FX's show, Archer.
The best part was how true it was to actual US history, like how George Washington sported 2 retractable gas powered chainsaws, or how Paul Revere was a cybernetic centaur, or how Benedict Arnold was really a werewolf who killed Lincoln while Lincoln and George Washington were at the Ford Theater. Very realistic.