Why did world war 2 become worlwide. Write 2 paragraphs in your own words

The second world war was only confined primarily to Europe and a small part in China. However, the war became world wide "officially" when the USA declared war on Japan and entered the war from the side of the allies.

USA got drowned to the war because the Japan attacked Pearl harbor in 1941. This surprise attack on American soil resulted in USA declaring war on Japan and Germany eventually declared war in USA.

Moreover, the war involved the nations from the British and French colonies in Asia and Africa as well.