I use the same little window unit I tried in my camper at home to cool my bedroom. It’s a really big bedroom, the house was built in ‘03, it’s got one of those “master suite” bedrooms in it.
That little thing, if you let it run a while, cools that whole place down really nice.
My camper has a metal roof that gets hot as blazes in the desert sun. That may be a contributing factor why it had a hard time in the camper.
If your window unit is up to the task, I’m sure you could build a proper platform to mount it securely.
Running both the window and the roof air really chilled the place!
I’m considering adding a second roof AC in the other vent. Overkill, certainly but where I go is in the middle of nowhere and redundant systems are a good thing. And overkill AC is great in a hot desert.