Burning jet fuel would be unlikely to melt steel into a liquid pool, but with a maximum burning temperature of 1796 °F, it would easily soften the steel to the point that a loaded steel structure would fail.

Your interpretation of the kinetic energy of the plane is a bit removed from physics, even though you are using some physics terms. The crash of the plane would certainly spread fuel quickly (think of a water balloon hitting something), but the conversion of the kinetic energy of the moving fuel into heat would not superheat the liquid into a gas. It would raise the temperature only a few degrees. The combustion of the fuel would, however, supply plenty of heat.

Here's a quick calculation, using water, which has a similar density and compressibiltiy to liquid jet fuel:

A 767 cruises at about mach 0.8, which is 272 meters per second. A kilogram of water moving that fast will have 36,992 Joules of energy (1/2 M v squared). I'll round that to 37 kilojoules. I'll cheat and use google to convert that to kilocalories (type: 37 kilojoules in kilocalories). 8.8 kilocalories. The specific heat of water is 1 calorie per gram, or 1 kilocalories per kilogram. That's the heat required to heat something by 1 degree C. So, if all of the kinetic energy of that water gets turned into heat and all of that heat goes into heating the water, the water will be almost 9 C warmer after the crash.

There are a few assumptions here. I'm assuming that all of the energy turns into heat and all of the heat goes to heating the water. To whatever extent my assumption is wrong, that means the water gets heated less. I'm also assuming that jet fuel and water have similar specific heats and densities. Even if they are different by a little bit, that isn't going to turn 9C into 9,000C.

Finally, I did this calculation for one kilogram. Of course there was more fuel than that, but the weights cancel each other out. Twice as much liquid means twice as much energy, but then you need twice as much energy to raise the liquid the same number of degrees.