You mean like Native American peoples like the Ojibwe, Hopi, and Navajo?

I recommend that you ask this over at r/asksanthropology. The nature of ethnicity and the creation/maintenance of ethnic groups are current and controversial topics in Anthropology.

Wouldn't the best example of "ethnic Americans" have been the American settlers of Texas. They were regionally encouraged to sterile to >In the news of the war in Crimea there was talk of "ethnic Russians"

What’s more, Crimea is not in fact populated by an ethnically Russian, pro-Russian majority. That’s far too homogenized an image of the peninsula. In fact, before annexation, Crimea’s Russian ethnic majority was highly fractured and contested https://www.washingtonpost.com/news/monkey-cage/wp/2015/12/03/do-crimeans-see-themselves-as-russian-or-ukrainian-its-complicated/

and there is writing about the ethnic Kurd population in Turkey.

Turkey’s ongoing struggling relationship with its ethnic Kurdish population has http://www.eurasianet.org/node/76621

So I'm curious about what could/would be an "ethnic American" population. I'm guessing America being newer and more of a melting pot than those other areas makes it a bit harder to pin down.

But, could there be an "ethnic American" population within Canada or Mexica? ... if so what would that look like?

to develop the area. And diffrences in culture and expectations led to conflict and those differences were based on the ethnicity of the people. Of course, I am simplifying it greatly but I think this example best shows what the op wants to ask.

The United States has a very different approach to ethnicity than the rest of the world does. No comparison really holds, and the topic can get politicized very fast. It's tricky ground. I sometimes work with defining ethnicities, I can very quickly try to clear some things up for you.

Ethnic Russians are Russian-Speaking people who self-identify as Russian. Under Soviet rule, large numbers of Russians were transferred around various Soviet Republics; in part to keep key industries controlled by ethnic Russians, in part to transfer skilled workers to less developed areas, and in part because what with Russia being the largest component of the USSR most people moving for whatever reason would be Russian anyway (and an even earlier diaspora already existed at the time of the Russian Empire). Although many of these people moved back to Russia after the breakup of the Soviet Union, many others stayed behind. The latter are what people mean when they talk about "Ethnic Russian" separatists in Eastern Ukraine: Eastern Ukraine was an important mining and industrial area to which many Russians were transferred.

The Kurds, on the other hand, are an ethnic group without a state. They have a language and culture, but have gotten the short end of the stick in modern politics, and haven't had a happy history of late.

An ethnic group is a group of people who share a culture, language, and identity. A single state can contain one or multiple ethnicities. Sometimes, defining an ethnicity is difficult (are Northeast Italians a separate ethnicity? Are Friulians? Are Südtirolers ethnic Austrians living within Italian borders? Are Austrians even an ethnicity, or are they just Germans with funny accents?)

In the United States, "Ethnicity" is normally a very broad term used for statistic purposes: White, Hispanic, Black, Asian and Other/Pacific Islander. When North Americans ask the question, "What are you?" the intended answer almost always refers to origins. A person answering, "I'm half German, and the other half is Irish and Italian" probably doesn't self-identify as German, Irish or Italian. American identity, after all, is an amalgamation of all the separate identities of people who immigrated to America (with a heavy-handed Anglo-Saxon foundation in the US and Canada). But what defines "American Culture" or an "American Ethnicity" isn't really a historical question, unless we're talking about ethnicities of Native American peoples like another user proposed. But I gather that's not the gist of your question.