Most likely you can because you have no record. However, if the US authorities learn that you did have a charge, they could decide to refuse you admission. The question is whether there is any method of them finding out.
There should not be because there is no record as stated. But, we really do not have a clear picture of what information is shared in the name of National Security and what is not. I do not believe Canada is sharing information on alternate measures but only because I have personally never heard of anyone having a problem.
But, the US is a foreign country and they can do as they please on the information that they have. What they do and why has nothing to do with Canada.
So, I suggest you try and find out. The reason I say try, is that you are inadmissible to the US if you merely admit to Border Security that you committed a criminal act. That essentially means there is no ability of finding out before hand because you cannot contact the authorities in advance to inquire. As soon as you tell them that you did alternate measures then they know and that will go into their system.
I doubt if you will have any problems. You can truthfully answer that you have no criminal record. If pushed as to whether you were ever arrested you can truthfully answer that you had been but the charges were dropped. As long as you do not admit committing a crime, there is no issue.
Border guards have huge discretion and even if they deem you inadmissible, they still can let you in for a spcific length of time and for a specific purpose. I recently had a guy who is now in his forties but had a marijuana conviction in his 20's. He had to go to New York for an important business conference. He was stopped but they allowed him in for 2 weeks then he had to be out of the country or face arrest. In this case, he was also told not to try again until he had a waiver.
A Waiver is a document that essentially states that the US will let you in regardless of the issue. But, it has to be applied for, takes about a year and a few hundreds of dollars.
In my opinion then, you are unlikely to have a problem. If you do, they still may let you in and if not, apply for a waiver. Certainly you must qualify for that!
I hope this has assisted you. If you need any clarification, just ask and I will respond. Otherwise, please rate my answer well for my time considering your question.