Copy & pasting the PLINE command works because the coordinates are what's requested immediately following the command sequence:
pline 3263923.0305,1263407.6526 @14.184<-156.7
But when it comes to the INSERT command (assuming your drawing does have a block named "arrow") since AutoCAD supports long file names which includes spaces it does not know when the block name ends.
This is why the Insert line from your Excel file does not work. AutoCAD thinks you want to insert a block name that includes all those numbers following arrow:
-insert arrow 3263923.0305,1263407.6526 -156.7
The way to do this is to use lisp which surrounds the block name along with the other entries with quotes like this:
(command "insert" "arrow" "3263923.0305,1263407.6526" "1" "1" "-156.7")
Now in a Script file the way to make it work would be to separate each entry into a different line like this:
-insert
arrow
3263923.0305,1263407.6526
1
1
-156.7