What is the meaning of Trouble in River City?

The phrase comes from a song in Meredith Wilson's The Music Man titled "Trouble" and also referred to as "Ya Got Trouble" or "Trouble in River City."

It is sung by the character Harold Hill (a con-man/traveling salesman pretending to be a music professor). Through the lyrics of the song, Hill persuades the parents of River City that the new billiard table in town is a threat to the moral fiber of the River City youth, verbally illustrating a catastrophic decline of conservative, turn of the century values. All this, of course, is setting the stage for his alternative, wholesome pastime - a boy's band - for which he will sell uniforms and musical instruments.

My interpretation of the phrase, as used today in a colloquial context, is that it refers to an exaggerated problem, or an unfounded, petty, mass hysteria. This of course, is open to interpretation.