noun
all over Japan; throughout Japan
Used to describe something that happens or exists across the entire country, often in news, reports, or formal contexts.
この商品は日本全国で販売されています。
This product is sold throughout Japan.
日本全国から観光客が集まった。
Tourists gathered from all over Japan.
全国 means 'nationwide' or 'the whole country' and can be used for any country, while 日本全国 explicitly specifies Japan.
Compound of 日本 (Japan) and 全国 (the whole country).