Although I enjoyed for what it was, it is an abomination to try to read anything of Heinlein's book in it. Only the vaguest of plot details and characters carry through and the message of Heinlein is completely, and totally lost in Verhoeven's film.
In the book, the 'bugs' were a highly technologically advanced race, who most certainly were a threat and most certainly had spaceflight. They had cities, for crying out loud.
Completely gone from the movie is the time the main character spends in officer training school. All lessons of values, honor, duty and morals are just gone from the movie.
BTW, the _Mobile_ Infantry is supposed to be mechanized with high tech, powered battle armor that puts them more on caliber with a tank division. They are not foot soldiers.
All that being said, the movie most clearly was a farce, but it was a terrible one and has very little in common with Heinlein's book of the same name.