Yeah, entry into the Land of the Free can be quite daunting.
I wrote an article here once about a Miami customs encounter that
was quite horrifying--3 hours of waiting, bad vibes, and endless threats
of arrest, like something out of a scary movie.
Another time a Customs goon trying to make the front page called
my Thai beach sand "organic matter" and wanted to have it tested until his colleague told him to cool off and shut up.
It seems the 4th Amendment is null and void when you arrive
into these United States.

Cops are like politicians in that they have mastered the arts of obfuscation and deflection. If you are absolutely dead-set in your mind that you will not consent to a search, beware. They turn around the question to: "Do you mind if I look in your trunk?" or "Do you mind turning on your cell phone?" In both cases, if you answered "No," you just gave consent.

Yeah but it gets worse.
Even if you say NO to the "Do you mind?" tricks they'll just
call in a dog who will give the desired spurious "alert" and they'll say it's legal.
Bottom line, if they want in, they're going in.
Sayonara, fourth amendment.
Check out "breakfast in collinsville" on youtube if you think cops don't pull this crap every day.

That wouldn't really work -- even if you inadvertantly give "consent" as a result of such word games, you can withdraw that consent at any time.

That said, US law enforcement are notorious for their attempts to pressure people into giving "consent." Happens all the time. As I related elsewhere in this forum, I had a CBP supervisor tell me point blank that I was not boarding my plane unless I "co-operated" (i.e., "voluntarily" waive my constitutionally-guaranteed rights). I held my ground, but 99% of people wouldn't.

As for the double negatives, I do get a bit of enjoyment out of answering questions like "do you mind if we ask you a few questions," or "do you mind if we have a look in your bag" with "yes." Invariably, they think I've just consented, and then I clarify "You asked if I 'mind', and in fact, yes, I DO 'mind' if you do. I mind very much -- good day." CBP will often take offence at this, and then I remind them that lying to an officer is a federal offence, so if I had given any response other than the truthful "yes, I DO mind" I could be charged with a felony.

I wonder how many people know that they can withdraw consent?

Good on you for sticking to your guns. I have said, "Are you asking me if I consent to a search?" before answering 'Yes" or "No." That sometimes throws them into a tizzy because they aren't used to Constitution-based push-back.