This might cause a bit of a row...
I-80/90 from Chicagoland to Ohio. Either build an alternate Free route for one of the Interstates or replace I-94 to Detroit and Pt. Huron with I-90, then reconnect I-90 to the system in Buffalo heading to Boston. Under this change, I-94 would terminate at I-90 at the Dan Ryan.
US-30/I-84 in Oregon. US-30 is not much more than a scenic route through Oregon, and should be largely eliminated. The western portion should become US-26, and US-26 should either become an extension of I-84 or I-505, with the portion after the freeway becoming an Oregon State Route.
I-96/I-275 near Detroit - FHWA already doesn't consider this in existence. Just remove the signs.