How did the attack on the Lusitania bring the United States closer to declaring
war in
1915?

The attack on the Lusitania brought the US closer to clan war in 1915 because Germany found a new way to attack, using a weapon called the U-boat, and they wanted to put an end to that. Early events in 1917 that cause President Wilson to declare war war events in Russia and the Zimmerman note.

the use of email to replace slower surface mail.

to act quickly in times of danger to the united states

because you have to act quickly if you want to live/survive.