Searching for John Phillip, Yugoslavia/Serbia (neither of which are Serbian spellings) in US records finds the following... do any of them sound like your Gramps?If not maybe you can tell us where in the US he lived?What was his birthdate?What was his spouse's name?
Charles John Popp United States Census, 1920 birth: 1882 Yogoslavia residence: 1920 ,? Summit,? Ohio spouse: Elizabeth Popp children: Tony Popp,? Alexander Popp...
John Popp United States Census, 1920 birth: 1878 Serbia residence: 1920 ,? Cuyahoga,? Ohio spouse: Anna Popp child: Louis Popp
John Popp Ohio, Deaths, 1908-1953 birth: 1866 Serbia death: 28 Nov 1920 Perry,? Stark,? Ohio burial: 02 Dec 1920 Massilon,? Stark,? Ohio residence: 28 Nov 1920 Summit,? Ohio John Popp
West Virginia, Naturalization Records, 1814-1991 birth: 1883 Shid,? Yugoslavia naturalization: 1940 Monongalia,? West Virginia,? United States
Then using Ancestry.com I find in the 1930 census:
John Papp [John Popp] Susie Granite City, Madison, Illinois abt 1878 Yugoslavia Head
[John Popp] Esther Granite City, Madison, Illinois abt 1908 Yugoslavia Head
Aha and here is an Ohio Death record for:
ame: Philip Popazivanov titles & terms: event: Death event date: 16 Aug 1925 event place: Cincinnati, Hamilton, Ohio residence: Cincinnati, Hamilton, Ohio street address: 3429 Fiffe Ave. gender: Male death age: 42y 4m 26d marital status: Married race: W occupation: Machinist birth date: 21 Mar 1883 birthplace: Hungary estimated birth year: 1883 burial date: 18 Aug 1925 burial place: Cincinnati, Ohio cemetery: St. Mary's Cemetery father: Samual Popazivanov father's titles & terms: father's birthplace: Hungary mother: Zivaca Martino mother's titles & terms: mother's birthplace: Hungary spouse: Minnie Popazivanov spouse's titles & terms: