Two things which probably added to the film's problems...

I thought this film was totally misguided and painfully unfunny (what was Schlesinger thinking?) but I'm wondering if the following also contributed to the critical mauling the film got:

1) The title song included the line 'It's America on wheels' suggesting the film was a satire on the entire country rather than small-town American life.

2) The director was not American.

I could understand viewers being offended by the impression that this was a foreigner laughing at America.

And before anyone assumes I'm an American who can't take a joke...

I'm English, I didn't think the film was funny at all and I can understand American cinema-goers reacting badly to it.