Is it just me?

Shorter hitch to axle distance reacts much quicker...you just over corrected, it happens.

No, it's not just you. The longer the trailer, the "easier" it is. We have a nearly 36 foot FW and DH backs it effortlessly. Fast forward and we purchased an additional camper, a small popup. Yeesh! I'm looking at my husband like "what the heck!" "can't you back that thing?!". Not so easy. Ha! First trip out we chose a pull through! At home he backs it up to a certain point, then we unhitch and move it the rest of the way by hand. Can't do that with the FW!

It's not just you... single axle trailers are notoriously sensitive to steering input. Use very minor corrections and go slow, slower, slowest. When towing my 10' cargo {motorcycle} trailer behind our Class C it is a challenge as I cannot see it in the mirrors until it starts to swing wider than I usually want/need.

If I angle the rear camera down to see the ball then I lose most of my view of the trailer - raise the camera angle for a better trailer view and I cannot see the ball. Might be time for a second camera.

:S

Happens to me too when I haul a strange trailer. Particularly shorter trailers

Very common as explained above, we have a similar sized TT and it is ultra easy to get it into any site. Our ATV trailer on the other hand just does not want to comply with my steering tactics, if I go very slow when backing I can get it somewhat close to where I actually want it to be. Sometimes I use it to go to the county dump to throw trash, the workers will point to a small opening between a couple of trucks and if I am lucky it takes me just a few tries to get it right.

Try backing up a lawn tractor with a yard cart attached. More times than not, I'll start backing up and then stop, get out and move the cart into position so I can back up another 5 feet

I have a 4’ X 8’ Featherlite trailer I keep under a carport.
It gets loaned all too often.
I always stress to be sure to call me when you bring it back so I have time to set up a lawn chair.
That thing will change direction and jack knife in two feet.

As stated above, it's perfectly normal what you experienced. We have a 10 x 6 bed utility trailer. It's so touchy backing up with my 22 foot long dually. It will jack-knife in a heartbeat. Well, after 5 years of owning the truck, it's definitely easier now backing that utility trailer. But it SURE does handle different than my prior 35 foot TT and now my 41 foot 5er.

As stated above, slight turning of the steering wheel, and slow, slow, slow.

I have a 12 ft. aluminum boat that I pull with a long wheelbase dually. I can back it into the water as I can see the top of the motor. I had to build a center bracket that sticks up with a tennis ball so I could see the trailer when backing back down the ramp. I find with short trailers that looking over my shoulder at a center point on the trailer I can pick up on minor movements and make corrections, using the mirrors, not so much.

Black Friday around here, you have to park on the freeway shoulder and hop the fence.

Is it just me?

No