Originally Posted by tonan

well this was easy, you are missing on the syntax

nawk 'NR==FNR{a[$1];next} {if($1 in a) print $1,"Found";print}' OFS="," File_B File_A

-----Post Update-----

sample output

bash-3.00$ nawk 'NR==FNR{a[$1];next} {if($1 in a) print $1,"Found";print}' OFS="," File_B File_A
NY,Found
NY
NJ,Found
NJ
PA
CA,Found
CA
VA,Found
VA
TN