Well, originally, I thought ethnicity refers to ethnic origin, which is defined as: "Of, relating to, or characteristic of a sizable group of people sharing a common and distinctive racial, national, religious, linguistic, or cultural heritage."
I didn't really see colonized countries (Australia, USA, Canada) as an ethnic origin because their populations do not really share a common racial, religious, linguistic, or cultural heritage... their populations are quite diverse in these categories. As opposed to being, for example, Chinese, where a large majority are South Asian, speak Chinese, celebrate Chinese New Year, have rice as a staple in their diet, etc...
Ethnicity is usually referred to as a racial or cultural heritage; I have never heard of it as a national heritage before, so I thought it was the wrong classification. But upon further research, I see I was wrong, it does include national heritage. My apologies.
Remember that Australia was once a British prison colony, so many of the names there may have originated in the UK.
This is kind of what I meant. While X may be Australian, X's ethnicity would actually be the UK origin (ie. German, Dutch) because only 2.2% of the people in Australia are actually "native" Australian, right? Most are the descendants of the Irish, British, etc. settlers. So their ethnicity would usually be listed as "of Irish descent" while they are proudly Australian.
