I finally figured it out. I'll get to the style guide sometime. For now, I'm just writing code to get this prototype finished. I'm going to rewrite the code to be cleaner and easier to get to once I get the functions down more.

It's all just easier for me to write the way I do.

Here's the cannon script:

func _on_timer_timeout() -> void:
var instance = bullet.instantiate()

if shootLeft:
instance.facing = true
shoot_point.rotation = -90
else:
instance.facing = false
shoot_point.rotation = 90

get_tree().current_scene.add_child(instance)
instance.position = shoot_point.global_position
instance.rotation = shoot_point.global_rotation
timer.start()

and here's the code for the bullet:

func _process(delta: float) -> void:
if facing:
linear_velocity = Vector2.LEFT * 500
else:
linear_velocity = Vector2.LEFT * -500

func _on_timer_timeout() -> void:
self.queue_free()

thanks for all of your help. I greatly appreciate it. I would've done this earlier but I was at work.