A sovereign state (a 'country' in common language) consisting of 2 or more nations (as in geographically defined, ethnic nationality) or even a sovereign state having 'at least one distinctive Nation within it', based on the example of Quebec , seems to be currently defined as a multi-national state, but I couldn't find a single word or even short phrase for the reverse: "a nation within a state", although this exact longer phrase is in frequent use, as the following Google search will show:
A few examples: Wales, Scotland, Brittany, Quebec (arguable), Ukraine when it was part of the former USSR (also applicable to all the other nations that once made up the USSR, later becoming independent states) and the Navajo Nation.
So what is a single word or short phrase meaning 'a nation within a state?'
Mandatory Example for SWR: Nation A is a __________ , which means that Nation A is a nation within a state.
Note: It is not enclave or exclave which terms instead deal with 2 or more entirely sovereign states.
Note 2: members are earnestly requested to please resist the temptation to engage in any political debate, and my question is concerned solely with the linguistic aspects of the matter.
 In 2006, the House of Commons of Canada voted in favor of Government Business No. 11, which states that the Québécois "form a nation within a united Canada".
Source: https://en.m.wikipedia.org/wiki/Multinational_state under the heading 'modern multinational or multiethnic states' - Americas - Canada.