I forgive you for being pedantic.
Just to be clear:
On the whole the ‘z’ alternative has nothing whatever to do with America;
The ‘z’ is etymologically correct (where used properly);
The ‘s’ principally came into use by those believing it (apparently wrongly) to be correct by analogy with...
When I was taught at comprehensive school, when it was first implemented, we were taught to use the s and it was implied that using z was an Americanism. I have since learned that this is not the case and that s was used in place of z when uneducated people got confused when taught English using...
Fair enough. I wasn't picking on your spelling I just find the use of z or s interesting. Some people say using z is an Americanisation but in fact it is how it was used in old English.