GarryB hypersonic cruise missiles are already in very very advanced stadium of work ,but the point continue to remain the same : an hypersonic missile with strategical range (at least in the league of today Kh-102) would have technical requirements and ,above all COSTS (in particular in reason the design solutions and very complex materials necessary to sustain the immense thermal, magnetic and kinetic sollicitations linked to high hypersonic speed regime for a very protracted span of time) that would produce a price tag for it not significantly lower than that of a startegical hypersonic bomber.
The fundamental problem is that a bomber flying at hypersonic speeds will not be able to manouver like a subsonic fighter, so that hypersonic bomber will be threatened by the same ABM systems threatening Russian ICBMs.
The purpose of a triad of nuclear weapons platforms is that no one measure will defeat all three legs of the triad... making the bombers fly high and fast makes them too much like slow SLBMs and ICBMs.
Another thing is that materials and technology including aerodyamics created for cruise missiles... even if they are only 1,000km range weapons that could be used to hit air bases and major Air Defence Network nodes in front of the bomber as it supercruises along at mach 1.5.
Taking things in steps allows the technology to mature... you might not ever want to have hypersonic bombers but for now they can be a long term goal with hypersonic cruise missiles as shorter term goals along with subsonic stealthy low flying cruise missiles.
Sure you could probably create one hypersonic bomber to replace all of those systems, but I think it would end up being too expensive for now... too big a step.
I realise that mach 3 bombers were tested in the 1960s... but flying at mach 3 wouldn't make you that much safer than being able to dash to mach 2 over the target area, but it is much more expensive and creates a lot of problems to be able to get to mach 3 and beyond.
I say again that a hypersonic bomber is a good long term goal because if we can deal with the problems and issues then a scramjet powered aircraft that can fly into orbit becomes a possibility... and that would be really cool.
I think a supercruising mach 1.5-1.8 bomber that might have a sprint speed of mach 2 or more but that carries long range subsonic stealthy cruise missiles internally and can carry 4 or 6 further hypersonic cruise missiles with ranges of 1,000-2,000km with scramjet propulsion for strategic missions would be the ideal.
A flying wing with horizontal tail surfaces (a bit like the YF-23 except using thrust vectoring and horizontal only tail surfaces) and new 5th gen bomber engines in the 35-45 ton thrust range that enables the aircraft to supercruise comfortably. Later modifications that can burn fuel in the bypass air allowing the engines to be used in a ramjet mode should enable high speed operation. Later developments in terms of scramjet technology will allow even higher speeds to be achieved.