Neither he nor his father appear in the 1920 census.
Right - Ameglio might have been misspelled.
Social Security Death Index:
SSN: 098-26-6713 Peter Ameglio, born 29 Jun 1916, died Jan 1981 at Monticello, Sullivan, New York.
SSN: 082-05-8170 Antoinetta Ameglio, born 1 Mar 1895, died Aug 1973 at New York, New York, New York
SSN: 157-24-5652 Dominic Ameglio, born 14 Aug 1933, died Aug 1974 at Dunellen, Middlesex, New Jersey
There is an Ameglio family in Brooklyn in the 1910 Census. Perhaps Giacomo was related to that family who was already there.
My source is Ancestry which allows me to post online content of "...unique data elements that are part of a unique family history or genealogy."
The 1920 US Census was started on Janaury 1, 1920, so Giovanna should be there, but apparently is not.
I do not see a Giacomo * married to a Giovanna * at all.
There's nary an Ameglio in the 1930 US Census. Jeez - now you see them, now you don't.
Here is a link to cemeteries in Sullivan county. Oh - buried in Long Island - never mind...
http://www.rootsweb.ancestry.com/~nysulliv/cemetery.htm