Blame it on alcohol. Have a few stiff drinks on the plane and make up your own countries. List every country you have ever been to.

Thanks everyone.
I think I'll take #10s advice but say that I ate the worm in Cancun and so clearly cannot be held responsible for anything. Like Vegas but with a bad sunburn. :D

<blockquote>Quote
<hr>Than there is the question whether 'forgetting' to write a country you visited on the customs form is qualitatively equal to making a willfully wrong statement, i.e. lying. I suspect it isn't.<hr></blockquote>
With all due respect, I suspect it is the qualitative equivilent. It reminds me of the Steve Martin comedy routine where he talks about what to tell IRS when they ask why you haven't filed tax returns for the last five years----I forgot..
If the government chose to prosecute for this offense (which they have never done and I doubt ever will) they would have to establish that the false representation was made knowingly. But how believable is it that you forgot you visited Cuba. Perhaps you could say that you did not understand what the form was asking, but even that is pretty lame and almost as unbelievable.
I did not say that one should list Cuba as a country visited on the Customs Declaration form. That is the recomendation of the National Lawyer's Guild. In fact I have often commented that unless one wants a confrontation with the OFAC, it makes no sense to make an unsolicited confession to a violation of the Cuban Travel Regulations by listing Cuba on the Customs Declaration form. The best advice for someone who is making an unlicensed trip is to follow the standard drill that has been repeated on this Board for years.
To directly answer the OP's question--- 1. It is not perjury to fail to list Cuba, but it is a potential criminal offense. 2. There are no reported cases in the Federal System of anyone having been prosecuted for failing to list a country on the Customs Declaration form. 3. In my opinion the government is not going to the expense of criminally prosecuting an ordinary citizen for not listing Cuba on the form.

Alta:
In some cases (like mine) one extenuating factor could be that the person in question is neither American nor of English mother tongue.
In any case and as you say it's pretty unlikely anyone will ever be prosecuted for 'forgetting' to list all countries.
With all due respect to Steve Martin, forgetting to file your tax returns ALTOGETHER and for 5 years IS in my view quite a bit different from filling out a requested form, but due a 'misunderstanding' ("I thought you were asking for the last country I visited") did not write down all countries you'd been to. And before they could even begin to contemplate whether they should take your case to the next prosecutory level they'd have to PROVE that you actually were in Cuba.
If you were careful that will (at least in the case of Mexico as gateway) be extremely difficult to accomplish.

Altahabana,
Thank you for providing the OP with good info regarding the possible downside to telling a little white lie to a US federal agent. While 9 times out 10 it's most likely not going to land you in much-if any-trouble. It very well could, IF (big if) you rub said agent the wrong way. Better to mind you p's and q's. You can always give us the finger after you clear customs/immigration.

# 14
I'm getting curious and will discuss the issue of whether an 'omission' has the same legal weight as an outright, deliberate lie with a defense lawyer friend of mine. I doubt it, but if it does indeed, the US the legal system would have to be ranked on a similar level as what they call 'democracy' here - i.e. (compared to Northern Europe at least) very, very low.
And a white (or other) lie isn't going to be any problem until it is PROVEN to be one - let's never forget that big brother has to come up with evidence; if you don't (stupidly) hand it to them, who will - the Mexicans (lol)?
BTW what is the meaning of "p's + q's" ?

#14 -- Please report back after you talk to the lawyer. If a form says "list every country" and you knowingly fail to list every country, I cna't imagine that that wouldn't be treated as a lie anywhere. If an income tax form asks you to list all your income, and you "forget" the $1000 you earned from an overseas account, is that OK in Northern Europe? In any case, it doesn't have a lot to do with democracy, which has to do with the form of government.
"Mind your p's and q's" = pay attention to details, be on your best behavior. There are lots of theories about the origin. The most credible is that it's advice to printers not to confuse a p with a q.

<blockquote>Quote
<hr>I'm getting curious and will discuss the issue of whether an 'omission' has the same legal weight as an outright, deliberate lie with a defense lawyer friend of mine. I doubt it,<hr></blockquote>
UNITED STATES CODE
TITLE 18 - Crimes and Criminal Procedure
PART I - Crimes
CHAPTER 47 - Fraud and False Statements
Section 1001. Statements or entries generally
(a) Except as otherwise provided in this section, whoever, in any
matter within the jurisdiction of the executive, legislative, or
judicial branch of the Government of the United States, knowingly
and willfully -
. (1) falsifies, conceals, or covers up by any trick, scheme, or
device a material fact;
(2) makes any materially false, fictitious, or fraudulent
statement or representation; or
(3) makes or uses any false writing or document knowing the
same to contain any materially false, fictitious, or fraudulent
statement or entry;
shall be fined under this title or imprisoned not more than 5 years or both
Why you continue to beat the dead horse? The OP was not asking how to avoid getting detected and charged with an OFAC violation. The best ways to do that have been discussed on this board for years and I suspect long before you made your first trip to Cuba.
The concealment of a material fact can be just as damaging as a deliberate lie---that is a pretty universal legal concept and one that is certainly not uniquely American. I would bet the omission of something important can be an element of some crimes even in Northern Europe.
Minding one's p's and q's means to be on one's best behavior.

#16
Will report back.
That's exactly the point: how are they going to establish that you did it 'knowingly'?
As a matter of fact, in Northern Europe it DOES make a difference if you merely 'forget' to mention some form of income in your tax return, or if you actually distort some figures - the latter is considered tax fraud and weighs a lot heavier than the former. Who's talking about an overseas a/c? That's adding another (and unnecessary) level of wrongful activity.
Read my message again and you will see that I am not lumping the terms 'legal system' and 'democracy' together but comparing them in the form of an analogy.

#17
If that's all so obvious - why do YOU 'continue to beat the dead horse'?
"
1) falsifies, conceals, or covers up by any trick, scheme, or
device a material fact;
(2) makes any materially false, fictitious, or fraudulent
statement or representation; or
(3) makes or uses any false writing or document knowing the
same to contain any materially false, fictitious, or fraudulent
statement or entry;
"
Before you worry me: PROVE that I used any trick, scheme or device, rather than innocently forgot (listen to the current crop of GOP operatives under investigation and you know what I mean - these folks certainly have the best lawyers $ can buy and are facing weightier charges than traveling to Cuba) to mention something.
Not mentioning something is not the same as making materially false, fictitious or fraudulent statements.
Who is using any false writing or document knowing the same to contain...?
If I forget I can't be 'knowing'.
But let's just leave the authoritative answer to this matter of contention to a real expert - which -and I suspect you- are not.