Welcome. Wagon looks great! As far as the wheels, it's all about personal taste. Some folks like traditional 15" wheels with plenty of sidewall. Others like something more modern with less sidewall. Personally, I think the wheels you have on there now suit the wagon well. If you go with the Challenger wheels, make sure you go with tires that are the right height. Tires that are too short or too tall can ruin the look of a car. Also, the offset on the Challenger wheels will require spacers, probably 1" to 1.5". Not optimum, but some people do it without issue.
A test fit of the wheels on the car shows no major fitment issue with the rim/offset. The oversize tires from the challenger even fit ok. I do need a smaller diameter/lower profile tire to clear the rear wheel house in turns. I'd probably be able to do the 255/35r20 in the front (about 1" diam bigger than 235/60r15), but it would be very close in the rear wheel house. I may need the 1" spacer to bring the offset out to clear. Well I need to buy tires for either set, so the 15's are getting the new rubber first.
The Challenger wheels should be about a -15 to -25 mm offset, while your 15" wheels are most likely closer to 0mm offset. So, the Challenger wheels will sit in further, closer to the suspension / frame. Did you try turning the wheel with them on? If so, I'm surprised they didn't hit steering components or the frame. Only reason I say all this is I speak from experience. I used to have a Dodge Magnum, which is the same platform, wheel offset, etc as your Challenger. And had test fit my 20" Magnum wheels on my '76 Montego, which uses a similar 0mm wheel offset as your Country Sedan. And had those issues. To make them work on the front would have required spacers.
I have had similar experience with the 17" Mustang wheels on the Fury. I have wheel spacers on my car. If they aren't on there the wheel won't even spin because of interference, let alone turn.