How far can a Super Hornet fly at max supersonic speed in a clean configuration?
An estimate:

An F-18E Rhino can only obtain its maximum speed of Mach 1.8 only at 36,000 ft in ideal air conditions and only in a clean configuration i.e. no external stores.

At 36000 ft at STP, Mach 1.8 translates to approximately 550 m/s or   1069 KTAS using the equations:

v = M*SQRT(g * R * T)

Where v is the velocity of the jet in m/s, M is the Mach number, g is the ratio of specific heats, R is the Ideal Gas Const. and T is temperature in Kelvin (use OAT at -40 C, 233 K).

Now an F-18E holds 14,400 lbs of fuel internally.  The GE F414 engine burns about 36,000 lbs/hr of fuel in full afterburner, so a total fuel burn of 72,000 lb/hr would be typical for this power output.  Assuming the Rhino could start at these altitudes and at Mach 1.8 with the tanks topped off, that gives us 14400/72000 = 0.2 hr or 12 minutes of flight time.  Ignoring upper level winds this would give us a maximum range of 213.8 NM.  

This might be enough to put warheads on foreheads, then run like hell back to friendly airspace and a tanker or a carrier but it's not very good for a long range cruise profile.