TileMapLayer doesn't move along with its parent node

I'm using Godot 4.4.1 and currently learning how to build auto dungeon generator. The dungeon "room" is developed using TileMapLayer.

Room parent are set to ColorRect for background.

I use this snipped in dungeon generator code to spawn new room:

func draw_map():
  for x in range(grid_size_x * 2):
    for y in range(grid_size_y * 2):
      if rooms[x][y] == null:
        continue
      var room = rooms[x][y]
      var draw_pos = Vector2(room["grid_pos"].x, room["grid_pos"].y) * room_dimension
      var instance = room_scene.instantiate()
      instance.position = draw_pos
      instance.doorTop = room["doorTop"]
      instance.doorBottom = room["doorBottom"]
      instance.doorLeft = room["doorLeft"]
      instance.doorRight = room["doorRight"]
        
      map_root.add_child(instance)

As written in the instance.position = draw_pos line, the spawned rooms are then moved to their appropriate location. However, as seen in screenshots below, only ColorRect is moved.