We need to use five QUERY functions, one for each set of columns, but then add something else to remove the blank columns. The following formula use JOIN and SPLIT:
=SPLIT(JOIN(",",IFERROR({QUERY({A2:C2},"select Col1, Col2, Col3 where Col3='USA'"),QUERY({D2:F2},"select Col1, Col2, Col3 where Col3='USA'"),QUERY({G2:I2},"select Col1, Col2, Col3 where Col3='USA'"),QUERY({J2:L2},"select Col1, Col2, Col3 where Col3='USA'"),QUERY({M2:O2}, "select Col1, Col2, Col3 where Col3='USA'")},"")),",")
Original answer (keeped here because this answer got an upvote before the OP comment)
The comma separator (or slash if the spreadsheet use a comma as decimal separator) is used as column separators. Replace the comma by semicolon.
=QUERY({A2:C2;D2:F2;G2:I2;J2:L2;M2:O2}, "select Col1, Col2, Col3 where Col3='USA'")