Do yourself a favor and be sure to get the trailer early. Like a week early. Be sure you have every thing you need to change a tire including bottle jack and blocks of wood. Go buy a spare tire and wheel and load it last onto the trailer. Do not rely on U Haul to do anything for you. Be ready to handle things yourself to save your trip. Also the lug nuts will have been tighten with a air wrench, be sure to have a breaker bar with to loosen them.
I travel 1,000’s of miles on the freeways yearly across the country. I see very, very few problems with U Haul trailers. However if something should happen it can take many hours for them to get to you and solve the problem.
Also if you have triple A always know where you are on the freeway. They want mile markers or exit numbers or they won’t help you.