Never used a REDFIELD or looked through one so I can’t comment on them, but I do own several Prostaff and Monarch models (scopes and rangefinder). However, when comparing the Monarch and Prostaff, I was hard pressed to tell the difference in glass (day/night), but (for me) the edge went to Monarch for tracking and repeatability. I haven’t tried the new Prostaff so I can’t comment on it.
Nikon has always taken care of any issues or questions that I have had and for the record, the issues were caused by me and not the product so for me, I wouldn’t hesitate to buy anything Nikon.
Don't get too caught up in American Made. I own Ford and Chevy vehicles all my life and they are not 100% American made.
I drive them because they are good vehicles, fit me well and I like’em and carrying an American name is a plus.
Anyway, I recommend that you look/compare them yourself, if possible and base your decision on what fits you best and reflect back to warranty, product reviews (others firsthand experience, not hearsay or such and such said), cost, etc.
It’s funny how a lot of people say “ You get what you pay for” which is not always true, sometimes you overpay for what you get, get more than you paid for, or even buy something you don’t need (guilty of this myself) because it’s cool/new which you will never really get full use of.
I meant for this to be a short post, but because of bashing, unnecessary comments,past experience, other threads, etc.... I got carried away
Good Luck on whatever you decide.