packages/usa-embed-container/src/usa-embed-container.twig
<div class="usa-embed-container" aria-label="16:9">
<iframe src="data:text/html,%3C!DOCTYPE%20html%3E%0A%3Cmeta%20charset%3D%22utf-8%22%3E%0A%3Cstyle%3E%0Ahtml%20%7B%0A%20%20background-color%3A%20black%3B%0A%20%20color%3A%20white%3B%0A%20%20width%3A%20100%25%3B%0A%20%20height%3A%20100%25%3B%0A%20%20display%3A%20flex%3B%0A%20%20align-items%3A%20center%3B%0A%20%20justify-content%3A%20center%3B%0A%7D%0A%3C%2Fstyle%3E%0A%3Ctitle%3E16%3A9%20aspect%20ratio%20example%20iframe%3C%2Ftitle%3E%0A%3Cp%3E16%3A9%20aspect%20ratio%20example%20iframe%3C%2Fp%3E%0A" title="16:9 aspect ratio example iframe" frameborder="0"></iframe>
</div>