[1] He attended the seminary in Vigevano before going to Rome to study at the Mastai College for Chinese Missions and Pontifical Urbanian Athenaeum De Propaganda Fide.

On 2 February 1912, Bonzano was appointed Apostolic Delegate to United States[2] and Titular Archbishop of Melitene by Pope Pius X.

He received his episcopal consecration on the following 3 March from Cardinal Rafael Merry del Val, with Bishops Pietro Barruti and Thomas Kennedy serving as co-consecrators, in Rome.

During his time as Apostolic Delegate to United States, Archbishop Bonzano sent $210,400.09 to the Holy See to ensure the 1922 papal conclave could occur.

[3] Pope Pius XI created him Cardinal-Priest of San Pancrazio in the consistory of 11 December 1922, whereupon he ceased to serve as Apostolic Delegate.