What was a major cause of world war i?

Immediate Cause: Assassination of Archduke Franz Ferdinand

The immediate cause of World War I that made the aforementioned items come into play (alliances, imperialism, militarism, and nationalism) was the assassination of Archduke Franz Ferdinand of Austria-Hungary

i think it was the assassination of someone important from Austria-Hungary

Explanation:

a. because the u.s. was the leading with the most technology, economy, etc. also was teamed with other allies witch boosted the economy and materials to improve technology and use it.