Your title belies your content
If it's fibeglas you'll know due to it having fibers loose in the crack.
Fiberglas repair is not fun. It might be worth asking a shop to do it.
Its easy, and it's worth learning, but it's a tough road when it comes to creating an acceptable finish.
Unless you have a plastic specific weld you want to do the material doesn't matter.
Here's the easiest way to repair it.
Buy metal staples, the kind made for industrial staple guns. t50 comes to mind.
Drill a hole at the end of the crack so it will not travel further, then Heat the staple to a dark glow and push the heated staple through the plastic like a frankenstein stitch.
Then you can finish it with glazing putty etc, then primer and paint.
There are PLENTY of youtube videos on the process.
Plastic welding is a skill acquired. You'll need clamps and backing plates and a special gun which might or might nor require an air compressor. Nothing much other than staples will hold that crack except plastic welding and if you're capable of that, you wouldn't be asking what you did. I have all of this equipment and welding would still be my last choice due to skill and time and general suckage.
You might want to contact the maker of your coach.
The cost might be less than you think for a new bumper facade.
It would be a shame to fix this if a new one is $300.
https://www.amazon.com/MAPM-Primered...9697513&sr=8-3
The link is to an incredibly(without proof I'd certainly lack credibility at this cheap) Cadillac escalade front fascia. $140 and FREE SHIPPING on a part the size of an escalade front bumper.
Consider bracing that backside by making an internal structure, lest you step on it and break it a apart again.
I would probably repair it by removing it, drilling holes at the end of the cracks, running a brace along the crack where I could, fill the crack with
Tough As Nails
Then spraying it with a spray can bed liner so it has an even texture, then painting to match or leaving it bedliner black if the contrast is acceptable.