YouTube videos not responsive

Hi, I am trying to embed a YouTube video on my site with the Supreme theme. No matter which way I insert the video onto the page, it does not become responsive. Most of my target market is mobile first, so I need to have this responsive.

I have tried inserting the video as the link, the embed link as well as the iframe, no luck.

I have also added this code to the CSS, with recommendations found online, but still not luck:
/* YouTube Responsive CSS for HubSpot */

.hs-responsive-embed {
position: relative;
height: 0;
overflow: hidden;
padding-top: 0;
padding-left: 0;
padding-right: 0;
}

.hs-responsive-embed iframe,
.hs-responsive-embed object,
.hs-responsive-embed embed {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
border: 0;
}

.hs-responsive-embed,
.hs-responsive-embed.hs-responsive-embed-youtube,
.hs-responsive-embed.hs-responsive-embed-wistia,
.hs-responsive-embed.hs-responsive-embed-vimeo {
padding-bottom: 56.25%;
}