A slight addition of mine in case your body has padding (to prevent the device from scaling to the body content-box, and thus still adding a horizontal scrollbar):
Depending on box sizing width 100% might not always be the best option. I would suggest
width:100vw;
overflow-x: scroll;
This can be applied in the context of body, html as has been suggested or you could just wrap the content that is having an issue in a div with these settings applied.
This is the code that worked perfectly in my Angular app that didn't show 2 vertical srollbars in desktop mode and didn't show the horizontal scollbar in mobile mode which was a result of trying the two top voted answers.