A "successful" counterfeit is anything that the crook manages to unload without it being traced back to him. It doesn't matter if the money is detected as soon as his victim takes it to the bank if, by that point, the crook is long gone.
By that standard, U.S. currency has some problems based on the fact that a decent printer could produce a fake that would withstand a quarter-second glance, which is all some money is apt to get in some transactions. In some venues where lots of cash gets passed around (certain swap meets, etc.) it wouldn't be hard to find a vendor who doesn't look too closely at cash; even if one is caught, if one has bought and sold enough merchandise before using the funny money, one would have plausible deniability (e.g. one could claim that one must have been given the fake note by someone else--one would be out the value of the note, but could likely dodge prosecution).
IMHO, currency should include some reflective or iridescent features that are visually obvious from any angle. I have no idea if the new currency does anything like that.
Won’t be long and paper money is going to include imbedded video shorts.
Yes. It does. You must REALLY not look at money.