The code you want to use is:
[U2B]*the end of the YouTube URL (in your example it's https://www.youtube.com/watch?v=
bpF__WvfwZ4*[/U2B]
You
don't want to use the URL tag.
Using the [U2B] [/U2B] tags works in all browsers. For whatever reason Chrome doesn't support just copy/pasting the URL.