Animoji Background No Longer Transparent

Greetings!

I used to be able to export Animoji Videos taken through iPhone's iMessage and drop them right into my Macbook's iMovie as an overlay. The exported videos went right in, without a background, similar to the way a png file would. I'd just use the picture in picture option.

Now, the Animojis comes with a black background. Is there a setting that I can change on my iPhone to prevent this from happening, or is there a quick way to remove the black background in iMovie to accomplish the same effect?

Thank you!