I'm sure the higher mileage on the OEM parts played a role in it. But I would say if the trailer and weight is distributed properly there should not be any issues with alignment.
That being said, if the alignment was off to begin with, I could see the added weight bringing it out faster and making it more pronounced.
For a bumper pull trailer, I would suggest the Equalizer weight distribution hitch. It may cost more but it is money well spent and the difference with and without is night and day. Your other option is the Firestone Ride Rite airbags. You can raise and lower them depending on the load to help balance out the truck.
I have both on my truck. I had the bags from when I used an open trailer but now with a 24' enclosed I use the equalizer and add to the bags just to smooth the bumps.