全国(quán guó) - the whole country, nationwide in Mandarin

全国 (quán guó) means the entire country taken as one unit. It attaches to almost anything with 的 or directly, giving 全国人民 the people of the whole country, 全国第一 first in the country, 全国范围 nationwide in scope. In news writing it is everywhere.

It sits in a productive family with the same 全: 全世界 the whole world, 全校 the whole school, 全家 the whole family, 全班 the whole class. Learn the pattern once and a dozen words come free.

The trap is which country. 全国 always means the speaker's own country, and in Chinese-language media that means China unless something says otherwise. If you mean the whole of Britain you must say 全英国; saying 全国 in a Chinese conversation and meaning the UK will be misheard every time.