I like it and would buy it. I like what it represents, the fact that on that day all our lives changed. No matter what we do in life or where we live it has impacted us in so many ways.
I don't think you should change the cross on the coin because here in the USA we have the freedom to have it if we want to. The "World Trade Towers" just happen to have been in the USA.
Therefore I say go for it.