I was meaning to ask something along those lines myself. What are we regarding as a "heavy bomber", since the definition has become rather cloudy since WW2?
Before and during the war, a "heavy bomber" was an aircraft that could carry more than 8000lbs of ordnance to distant targets, and were, generally, the largest aircraft around.
But then the lines of distinction started to blur as even fighters were capable of carrying the 2000lb of ordnance that previously categorised "light bombers".
More recently, the definition of "heavy bomber" has been regarded as an aircraft with a range greater than 8000km or capable of carrying nuclear ALCMs.
If we use the yardstick of ordnance payload or ALCM-carrying capability, many modern strike aircraft, technically, fit the definition of "heavy bomber". The F-15E can lift a weapons payload in the region of 24000lbs, although it lacks the "legs" to reach those distant targets. The F/A-18 is capable of lifting nearly 18000lbs and is equipped for launching ALCMs.
[As a side note, the practice of using aircraft as platforms for launching cruise missiles seems to have been abandoned, especially in the two most recent US offensives, in favour of using ship-launched and sub-launched cruise missles instead. Why waste jet fuel and risk pilots and multi-million dollar aircraft when you don't have to, right?]
However, if we opt for the basics of the traditionally accepted definition of a "heavy bomber" i.e. extreme range and large size, the list suddenly shrinks dramatically.