Is there a way to play FGO JP in NA?

You have to get an apk and use it to download the JP version.

You can download it online, I can't guarantee it that it will be updated though.
You can also create a Japanese Google account. It will be a lengthy process, but it will guarantee the app will be up-to-date.

The easiest method that I recommend is to just look this page up
http://fate-go.cirnopedia.org/summon.php

Take the banner you want, add it by 2 years, then it will arrive in NA around that time.

Look up QooApp if you're on android, if you're on apple you'll have to start a JP iTunes account

QooApp is the app i use to play both NA and JP versions, since i'm from EU and NA's regional restriction prevents people outside of USA to download it and play from Google Play.

QooApp is basically the same as Google Play but with .apk files without regional restrictions, meaning that you can play any game you want, as long as your phone can handle it. And they're very fast with the updates. I've never had a delay with FGO NA or JP and any problems in updating them from the app itself. This isn't illegal and DW/Aniplex won't ban you for using this.