The colonial period of any country is a time of:

 A colonial period is a period of time in a nation's history when it was under the control of a colonial power. One example is when the U.S. Colonies were under control of the British government before the Revolutionary War.

although world war i began in 1914, the united states did not join the war until 1917. the additional firepower, resources, and soldiers of the u.s. to tip the balance of the war in favor of the allies. remaining neutral. when war broke out in 1914, the united states had a policy of neutrality.