Without the assassination the war probably would not have occurred as suddenly as it did.
Furthermore, pan-Slavism would be the major cause here, as it led to the assassination leading to the political turmoil ending in all out war.
This showed that the Kaiser was pushing already rocky relations with Britain further in order to become the number one empire in Europe and hence gain power and superiority, shifting the balance of power in Europe.
This led to Britain’s hostility towards Germany and in turn its willingness to go to war in 1914.
Germany would have tried anything in order to explain, even if it meant threatening war.
On the other hand, militarism was also a major contributing factor leading to WWI.
However, imperialism was not the leading cause of World War I and was an important factor, however, not the main cause.
Imperialism is not one of the most important causes of World War One.
Other major factors such as the alliance system played a bigger role in bringing about World War One.
For example, the creation of the Triple Alliance between Italy, Austria-Hungary and Germany in 1882 led to Russia being excluded and eventually joining a ‘dual entente’ with France whom later joined up with Britain to form the Triple Entente in 1907.