state
Emphasizes a country's government or political authority, not its land or people; used in phrases like 'head of state' and formal or legal contexts such as international agreements; sounds odd for casually asking where someone is from.
强调一国的政府或政治权力，而非其领土或人民；常用于“国家元首（head of state）”等固定搭配以及国际协议等正式、法律语境中；若只是随口问对方来自哪里，用这个词会显得别扭。
The head of state signed the treaty on behalf of the government.
国家元首代表政府签署了这项条约。
country
The everyday, neutral word for a nation as a geographic and political place; used when asking where someone is from or naming places on a map; far more common in casual speech than 'state' or 'nation'.
表示“国家”最常用、最中性的词，指地理和政治意义上的一个地方；常用于询问对方来自哪个国家或在地图上指称某地；在日常口语中比 state 或 nation 都更常见。
Which country are you from, and what language do you speak there?
你来自哪个国家？在那里说什么语言？
nation 本词
Highlights a country as a body of people sharing an identity or culture, often in collective or emotional contexts like celebrations, mourning, or patriotism; less common for simple geography or government matters.
强调国家作为拥有共同身份或文化的一群人，常出现在庆祝、哀悼、爱国等带有集体情感色彩的语境中；用来谈论单纯的地理位置或政府事务时不太常用。
The whole nation celebrated together when the team won the championship.
整个国家在球队夺冠时一起庆祝。

State, country, and nation can all mean a country, but focus differently: state stresses government and political power, country is the common, neutral word, and nation stresses the people sharing one identity. State also means a part of the US; not compared here.

state、country、nation 在表示“国家”时都可译为汉语的“国家”，容易混淆，但侧重点不同：state 强调政府或政治权力，country 是最常用的中性说法，nation 强调作为一个整体的国民或民族认同。注意：state 在英语中还常指美国等国内部的“州”（如 California is a state），本卡不比较这一用法。