I\'ve included two below scripts in my header and I get the error \"You have included the Google Maps API multiple times on this page. This may cause unexpected errors.\
I know that in my case it's not a Rails app but might help to someone else ... I'm working with React and I was getting the same error when I was switching between views/pages.
And like wLc said window.google = {} worked like a charm and was deleting the error in the console but the tag was remaining in the html and was added every time I was revisiting the page that has the map.
On componentWillUnmount I've added some code to remove the tag.
const allScripts = document.getElementsByTagName( 'script' );
[].filter.call(
allScripts,
( scpt ) => scpt.src.indexOf( 'key=googleAPIKEY' ) >= 0
)[ 0 ].remove();
window.google = {};