ANSWER: LISP recursion using car/cdr

(defun natos-englishs ()
  (list '(Alfa Bravo Charlie Delta Echo Foxtrot Golf Hotel India Juliet Kilo Lima Mike November Oscar Papa Quebec Romeo Sierra Tango Uniform Victor Whiskey Xray Zulu)
        '(A B C D E F G H I J K L M N O P Q R S T U V W X Z)))

(defun convert-nato-english (item)
  (destructuring-bind (natos englishs)
      (natos-englishs)
    (cond ((member item natos)
           (nth (position item natos)
                englishs))
          ((member item englishs)
           (nth (position item englishs)
                natos))
          (t
           (error "Unvalid")))))

(defun -mapcar (function list)
  (if (null list)
      nil
      (cons (funcall function
                     (car list))
            (-mapcar function
                     (cdr list)))))

(defun format-lists (function lists)
  (format nil "~{~{~A~}~^ ~}"
          (-mapcar (lambda (list)
                     (-mapcar function
                              list))
                   lists)))

(defun conve (english-lists)
  (format-lists (lambda (english)
                  (string-capitalize
                   (write-to-string
                    (convert-nato-english english))))
                english-lists))

(defun convn (nato-lists)
  (format-lists (lambda (nato)
                  (write-to-string (convert-nato-english nato)
                                   :case :downcase))
                nato-lists))  

(list (conve '((P R O)
               (L A N)))
      (convn '((Papa Romeo Oscar)
               (Lima Alfa November))))

("PapaRomeoOscar LimaAlfaNovember" "pro lan")