You might also try adding defer to your script tag
<script defer src="https://maps.googleapis.com/maps/api/js?key=[MY KEY]&libraries=places"></script>
Bonus - you can also move your function to python
from anvil.js.window import google
class Form1(Form1Template):
def __init__(self, **properties):
# Set Form properties and Data Bindings.
self.init_components(**properties)
google.maps.places.Autocomplete(anvil.js.get_dom_node(self.address_box))