For some employers (not all), the ranking of your university matters very much, and they will not hire you if you did not attend a uni ranked above X (top 10, top 15, top 50, etc.) Some also pay attention to how your uni ranks/its reputation for a specific major - and that's independent of where the uni ranks as a whole.
In addition, if your uni is one of the strongest in your state, or region; but isn't one of the top in the US, then some "education sensitive" employers will note that.
But most employers don't care. And if you go to a lower ranked uni, there's a lot you can do to turn that experience into a "top tier" experience - take honors classes, do independent studies, take on leadership roles, do internships, get involved in a professor's research, do a student exchange - it's all there for you, if you're interested.