Johanna was not married when Joseph was born. In these cases very often the father is not named. MAYBE it is the man she married later, Sauer.
Parish Hausbrunn is not online now. You can try to send a mail to: firstname.lastname@example.org
Take a look at www.familysearch.org
New York, Passenger Arrival Lists (Ellis Island), 1892-1924 listed
Josef Ratsel 30y from Hohenau arr: 20.4.1911
more siblings of John?
Hattie Retzl * 13.9.1914 Bettendorf, Scott, Iowa f: Joe Retzl, m: Frances Retzl.
Wilma Retzl, * appr 1913 Scott, Iowa. f: Joseph Retzl (Austria) m: Fannie Retzl (Czech.), brother: Hans 8y (Austria)
Joseph´s mother Johanna married a man called Sauer.
? John F.W. Sauer (birth Austria) oo 11.11.1915 in Augusta, Des Moines, Iowa Fannie M. Schirmer.
father: John Sauer, mother: Johanna Raetzel
? John Sauer + 2.5.1969 in Santa Barbara *10.6.1890 in Austria. mother: Retzel