People
More than ever before, Americans are suffering from back problems, back taxes, back rent, back auto payments.
— Robert Orben

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
A wordplay joke that lines up 'back' problems with back taxes, back rent and back payments. The pun makes everyday money worries sound like an epidemic of aches, so financial debt and physical soreness pile up under the same little word.
Context reviewed