Want to blow some treasury change then fire missiles and take out a US Reconnaissance Aircraft. It was just after the Vietnam war conflict. Pilots came to an airshow featuring the SR-71 and a question came from the crowd.
Were you ever or almost shot down flying over Vietnam?
One pilot had a wry smile and said no! He did elaborate further with his closest call in an SR-71 on recon patrol over North Vietnam.
He elaborated, "The adversary has a devastating weapon nicknamed the SAM missile or Surface to Air Missile. Pilots would often refer to them as flying telephone poles. The closest call I had was during one such flight as my radar picked up a pack of flying telephone poles coming at the SR-71. Having no defensive countermeasures, our training said to put the pedal to the metal engaging afterburner mode.
Was I endanger? Yes, and no. Yes because they were entering my flight level and no it was the SR-71 which did not have stealth or needed it back then. It had exceptional speed as the brochure indicates that of Mach 3+. The brochure is correct it does go Mach 3+ but fails to define what the plus stands for and that that is only known by a few on the ground or in the air. I hit the "plus throttle" and watched in amazement how blips on the radar dropped off the screen. The SR-71 flew almost through China before I turned around and came back for refueling."
In 1971 there was speed before stealth as an SR-71 flies faster than a speeding bullet. These many years later the U.S. has had almost sixty years to make something more advanced in every aspect to the SR-71's capabilities. Satellites and newly developed drones are replacements for the SR-71. Does the US need a vastly improved version of the SR-71? NASA had its hands on a few since the 1990's. A futuristic SR-71 would skip off of space and back to the atmosphere for look at the ground. No need for a fighter jets going that fast because missiles would carry the "fight load" going faster than even a ramjet. If speed is the combative determiner then no pilot would be needed in the air frame. The pilot would be in some basement complex at a military base near you.
The last sixty years of black projects the industry has moved the standard into new realms where the SR-71 remains a modern marvel made by people before computers were available.