Re-entering US on B-2 visa after leaving over Mexican border without stamp

So your questions boils down to: "should I pretend I exited the US within the allowed time, or should I be truthful and admit the one-day overstay?".

If you try to pretend you exited the US at a different date from the actual one, CBP or consular officers will ask questions and possibly require a bit of proof. A plane ticket out of Mexico, hotel invoices in Mexico, the rental car agreement if you used one, charges on your credit card...

You won't be able to show any of that for the date you want to pretend you exited the US. On the contrary, there will probably be quite a bit of evidence against you. Whether they'll find it on their own or not will probably depend a lot on what you actually did. But don't be surprised if they do (it's actually quite probable that you will give them the information yourself without even noticing). And if you lied, you'll get banned.

I understand your current plan is to apply for ESTA, and collect documentation to have with you on entering the US. It is worth thinking about issues that might arise, and prepare information for each of them:

• When did you leave the US? For this, you want evidence showing that you were outside the US as soon as possible after you actually left.
• Were your activities in the US permitted for a B2 visa? The very long stay suggests something other than tourism, possibly work. You need evidence of actual tourism, plus means of support other than working.
• Are you trying to effectively live in the US while pretending to be a visitor? You need evidence that you really live somewhere else (family, job, university studies, own or rent a home...).

As stated by @jcaron in comments, nobody here is going to tell you to lie to a CBP officer. In the days before 9/11, it was very common because the databases were not properly synchronized.

Folks from my country would come and visit for one year, and when they returned to my home country would get entry stamps indicating they left the USA after a month or two. Those days are long gone. The databases are better synchronized for CBP officers to have exit information within a few days of departure. It is still not perfect, however it is pretty darn good.

First of all your B visa is automatically voided because of the overstay, it is no longer valid. Thus you cannot even use it, if you try and it is discovered you will immediately be sent back and receive likely a 5 year ban. But if it is discovered and you lie, that will be misrepresentation/fraud and you will be sent back with a permanent ban to reentry.

The choice is yours to be honest not only because it is the right thing to do, but because the risk/rewards are heavily skewed out of your favor. In your case IMHO it is better to apply for a fresh visa and come clean, one day overstay can easily be forgiven. The problem I see you facing is you have spent a lot of time in the USA in one shot, approximately nine months with one month break in Canada. That doesn't look like a true visitor. You will likely have problems if the consular officer notices that.

If you do choose to apply for an ESTA, be truthful on the application. The ESTA may honestly be the best chance for you to fly under the radar however even that is not guaranteed to get you in if you're questioned by an astute CBP officer at the border.

all the previous comment is very wise and correct. I'd try to apply for esta again, answering truthfully to the questions, you may have a denial but that's a 14$ loss. At that point apply for a B2 again. Mind that 1 day overstay may gives you problems (maybe not), but all the other options may cause you big problems. Good luck