Mecanica Nacional is to me a very clear example of a tragic-comedy. It has a linear narrative with a lot of funny situations and extravagant characters and at the same time, its turning point is a sad and tragic event: The death of the grand mother Dona Lola.
The humor in the movie is mostly synical. The characters make fun of Mexico, mexicans and Mexico-USA politics while they inpersonate the sterotypes they are making fun of. For example, when all Euebio's friends were expalining to Gregorio why it was good to cheat they ended up going around in circles and laughing about themselves and about how absurd there arguments were. It was not clear to me whether the director was making a critique of Mexican society or if he was just making a commentary on the multiple layers, contradiccions, and contrasts embedded in the culure and social politics of Mexico.
There were many social issues mentioned in the movie but none of them were fully developed. Some of them were: Machism, violence against women, traffic, social indifference, sensationalism and lack of self control. Some topics were more prevalent than others but none seemed to bother any of the characthers. It almost appeared to me that the characters needed to have all the defects they had to be funny and for the movie to make sense. I think that if any critisism was intended by the director it had to do more with the audience's reaction than with the characters themselves. If the audience could identify itself or its neighboors in the movie, then the audience would be accepting the director's portray of mexico and therefore the director would be attacking the audience. Some times we can only identify our own defects when they are reflected in other people and I think that the director makes it obvious that some of the behaviour of the characters was wrong.
Some of the scenes in the movie are also very foreign to the narrative and therefore I would suggest that they are there to point out that some sort of social commentary is trying to be made. I am specifically reffering to the couple wearing white. They first appear very clean and tidy and slowly become very dirty as the movie progresses. I would say that the couple is trying to show what is happing in the movie and specially how the behacivour of the characters has spoilt the trip which was supposed to be fun. Another of these foreign scenes are the takes of the traffic vs the race which can have a methaphorical meaning of the crowded city life of the family vs the fun and spontaneity of the country side.
One last thing! The movie also presents some positive aspects of mexican culture . Mexican people were shown as solidary, simple, family oriented individuals with a big sense of humor and hospitality.