If Hi Camille - welcome to Gente!
If you have exhausted all US documents then I would suggest your next step be to write to Italy and request records from the comune.
You may however prefer to search using the microfilms available (filmed by the LDS Church) at the family history center. They not only have the civil records for the comune but church records as well.
Civil Records - Registri dello stato civile di Capua (Caserta), 1809-1929
Church Records - Italy, Caserta, Capua - Church records
Title search results
Select a Family History Center to filter the results:
[ Family History Library (2) ]
Kirchenbuch, 1820-1825 Österreich. Armee. Garnisonsspital Cremona (Lombardie)
Kirchenbuch, 1821-1826 Österreich. Armee. Filialfeldspital 07
Are you familiar with how to order films and use the Family Search
website? If not, let us know and we can walk you through it.