Why did some Americans think the Zimmerman telegram was fake

Some suspected the telegram might be a forgery to manipulate America into the war.

Explanation:

On March 29, 1917, Zimmermann gave a speech in the Reichstag confirming the text of the telegram and so put an end to all speculation as to its authenticity.

the indians crossed artificial boundaries, setting the stage for conflict

answer: secession

secession, as it applies to the outbreak of the american civil war, comprises the series of events that began on december 20, 1860, and extended through june 8 of the next year when eleven states in the lower and upper south severed their ties with the union. the first seven seceding states of the lower south set up a provisional government at montgomery, alabama. after hostilities began at fort sumter in charleston harbor on april 12, 1861, the border states of virginia, arkansas, tennessee, and north carolina joined the new government, which then moved its capital to richmond, virginia. the union was thus divided approximately on geographic lines. twenty-one northern and border states retained the style and title of the united states, while the eleven slave states adopted the nomenclature of the confederate states of america.

explanation: