The US currency could be in for more trouble, of quite another kind.
The US is pretty much the only country whose currency bills all have exactly the same shape, size and colour, regardless of denomination -- from $1 to $100.
Actually, in recent years it's almost the same colour. Many were upset a few years ago when delicate pastel shades of other colours were introduced atop the green $20 notes (and, more recently, other notes), but you have to strain to make out the other colours: the visually impaired wouldn't be able to. Indeed, the blind or nearly-blind can't distinguish the notes in any way. (The 2004 biopic of Ray Charles, "Ray", portrayed the blind singer in his younger days demanding to be paid in $1 notes, since he wouldn't be able to count them otherwise.)
Now, in response to a lawsuit launched by the American Council of the Blind, a US appeals court has declared the near-identical nature of the notes to be discriminatory against the blind.
What happens next will be very interesting... I wonder whether, rather than resize or recolour the notes, the US Treasury will choose to emboss the denomination in Braille? Will that be possible or practical?