[meadsjn]

For want of a nail, the shoe was lost,
For want of the shoe, the horse was lost,
For want of the horse, the rider was lost,
For want of the rider, the battle was lost,
For want of the battle, the kingdom was lost,
And all for the want of a horseshoe nail!

[LibertyAndJusticeForAll]

Most appropriate, thanks.
I found this variation attributed to Benjamin Franklin, but it appears to be a Nursery Song and an old proverb or cautionary tale, (but not memorized by enough Americans).

For want of a Nail the Shoe was lost; for want of a Shoe the Horse was lost and for want of a Horse, the Rider was lost; being overtaken and slain by the enemy, all for want of Care about a Horse-shoe Nail.
- BENJAMIN FRANKLIN, POOR RICHARD'S ALMANACK