os.system('cls') messing with my loop? Loop is fine without the clear screen command. Can someone explain?

import random
import os # os CLS function messing with loops

card_names = 'two,three,four,five,six,seven,eight,nine,ten,jack,queen,king,ace'
card_names = card_names.split(",")

card_range = ['2','3','4','5','6','7','8','9','10','J','Q','K','A']
hearts = [card + ' of Hearts' for card in card_range]
spades = [card + ' of Spades' for card in card_range]
clubs = [card + ' of Clubs' for card in card_range]
diamonds = [card + ' of Diamonds' for card in card_range]

# find utf-8 code for corresponding symbols for display.


deck = hearts + spades + clubs + diamonds
player_hand = []
opponent_hand = []
opponent_guess_pool = []

def player_draw(): # working
    drawn_card = random.choice(deck)
    player_hand.append(drawn_card)
    deck.remove(drawn_card)

def opponent_draw(): # working
    drawn_card = random.choice(deck)
    opponent_hand.append(drawn_card)
    deck.remove(drawn_card)

def new_hand(): # working
    for player_hand in range(0, 5):
        player_draw()
    for opponent_hand in range(0, 5):
        opponent_draw()

def game():
    new_hand()
    player_points = 0
    opponent_points = 0
    while True:
        while True:
            if len(deck) != 0:
                #os.system('cls') # Problem with clear screen command
                print("Drawing card...")
                player_draw()
                print("Your hand: \n"); print(player_hand)
                print(opponent_hand)  # TEMP----------------------->
                player_guess = input('Guess a card: > ')
                print(player_guess)  # TEMP-------------------------->
                if player_guess in opponent_hand:
                    player_points += 1
                    print(player_points) # TEMP----------------------->
                    opponent_hand.remove(player_guess)
                    player_draw
                elif player_guess not in opponent_hand:
                    if player_guess not in deck:# or player_guess not in card_names:
                        print ("That's not a card I've ever heard of...  Guess again!")
                    else:
                        print("Go fish!")
                        player_draw()
                        print("Your hand: \n"); print(player_hand)
                        break
            else:
                game_over()

        while True:
            if len(deck) != 0:
                opponent_draw()
                opponent_guess_pool = player_hand + deck
                opponent_guess = random.choice(opponent_guess_pool)
                print("Hmmmm I pick... {}!".format(opponent_guess))
                if opponent_guess in player_hand:
                    opponent_points += 1
                    player_hand.remove(opponent_guess)
                    opponent_draw()
                else:
                    print("No??? awwwwww lame.  Guess I have to go fish.")
                    opponent_draw()
                    break
            else:
                game_over()

def game_over():
    while True:
        if player_points > opponent_points:
            print("You win!")
        elif opponent_points > player_points:
            print("Beter luck next time!  You lose.")
        else:
            print("We tied! No way! I guess we'd better play again!")
            new_game = input("Do you want to play again?(Y/n) >").lower
            if new_game == "y":
                game()
            elif new_game == "n":
                quit()
            else:
                print("You must enter Y or N")


game()