=query(A:B,"Select A, Count(B) where A is not null and B='A' group by A,1")

={"Data", "Count Amount";
 ARRAYFORMULA(QUERY({UNIQUE(A3:A),
 IFERROR(VLOOKUP(UNIQUE(A3:A),
 QUERY(A:B, "select A,count(B)
             where A is not null
               and B='A'
             group by A
             label count(B)''", 0), 2, 0), 0)},
 "where Col1 is not null"))}