Hi Giorgio
My apologies for chiming in rather late, but it appears you have been given some good information regarding this American soldier.
A few more details I would like to add which may be of interest. Your soldier was a member of the 2nd US Artillery Regiment, we can tell that by the number 2 above the crossed cannons on his M1872 Forage Cap, this basic hat design stayed in service with the US Army with minor modifications until 1895, when we adopted a circular bodied hat with a flat crown. We cannot know his Battery letter as it is obscured by the upturn of the cap's visor.
The hats were constructed of dark blue wool, with a black painted leather visor and chinstrap. Two, small gilded brass, General Service buttons held the chinstrap in place. No branch of service piping appeared on this pattern hat, only the service branch insignia which was worn on the front of the hat designated which branch the soldier belonged to.
The 2nd US Artillery appears to have been based out of Fort McHenry Maryland during the later years of the 19th Century, with individual Batteries being assigned to different stations in an as needed situation. Perhaps this young man had his likeness taken prior to a depature for a distant post in the American West, or the Labor Riots in Central Pennsylvania in the 1880's.
Whatever the reason was for his photo to be taken he was an American Soldier, neither Northern Agressor or Southern Slave Holder. No doubt his parents and older family members would have vivid memories of the great American disaster during the years 1861-1865.
In a few days the 17th of September will come round, perhaps some of us can take pause and mourn for a moment, that 150 years ago to the day, near 23,000 Americans managed to slaughter and maim one another at the Battle of Antietam, or Sharpsburg to our Southern brothers. The single bloodiest day in American Military history.
The War's over....
Larry