If you were going to perform in the States would you feel compelled to change your material any?
We are just talking about the jokes/one-liners right? and not the magic effects?
Assuming this is so, I suspect that the issue isn't just an international one, it is also a regional one. I daresay there are jokes that are told to audiences in the north of England that have more chance of going down well than in the south (and vice versa).
As Mandrake said, much of how the joke goes down is in the skill of the telling, but I do not think you wish to be taken into account. I believe you are referring to the concept of the the same comedian telling the same joke in two places and getting a totally different reaction in both places.
If this different reaction is not just a one off occurance (and let's face it all audiences react differently) then it has to be a cultural thing, and yet how could the "snail joke" possibly be catagorised in that way? I mean you would go to America and start telling jokes about Scousers/Geordies/Cockneys etc, but you might try to find if there is an equivelent area of America. I suspect that a Cockney joke may relate quite nicely to the bronx? but I don't think this is what Mr. Higley is asking.
I mean why didn't the snail joke go down well?
Well one answer is that it has nothing to do with the culture of the US and the UK, it is simply that your friend has no sense of humour.
I would say that as magicians, for the most part our comedy is limited to one-liners, or at least short quick fire jokes and as such we use lines that make us, the performer laugh. If you didn't think it was funny, you wouldnt use the line. (actually, if you didn't think it was funny, you probably couldn't deliver the line anyway). So, no. I don't think we should change our act.
Having said that, if you are English and you start a tour in the US and your funny lines were consistently getting blank unsmiling faces, then you would adapt. You would either leave the lines out, or hopefully by then you would have been in enough Stateside social situations to work out a few lines that do work.
I'm rambling. Does this one work in the US and UK?
Q: What is the quickest way to kill everyone in the circus?
A: Go straight for the juggler.