It goes horribly, horribly wrong.
Then he decides to lower the 1.8×1013 tonne, Manhattan-sized chunk of iron down on the ground. I'm considering the desert southwest in the USA; he buys land out in the middle of nowhere.
As soon as the magic lifting-and-integrity-maintaining field lifts off (if it never kicked in, the asteroid lands as a firestorm several tens of kilometers wide, scouring half the West US clean of life and probably triggering a nuclear winter), about two thirds of your average asteroid will crumble on the ground. But that's not enough, the asteroid doesn't spread on a wide enough surface. If it's "solid iron", scrap the two thirds - the asteroid will at most break in three or four pieces, tops.
We now have a mass of very dense material on the surface, and the crust cannot take the strain. The If the crust was thin enough you would get a puncture and a lava lake several kilometres across, as well as some really fierce earthquakes.
Unfortunately, the crust is not thin enough and doesn't fracture - yet. Rather, it starts bending and sinking in the middle - the process will take days or, hopefully, weeks, giving time to evacuate the whole West coast and Japan, New Zealand and the Philippines. Not nearly enough time of course; deaths number in the tens of thousands by relocation shock and accidents alone, and there will be several hopefully minor quakes. It's possible we'll have already lost Los Angeles at this point, but then again, maybe not. Yet.
The key phrase here is unfortunately "lithospheric bending dominates over fracturing". Bending is very, very bad news.
After some time, the strain exceeds the crustal resistence. Fracture ensues, the asteroid is lost to the depths of the mantle, and an area several kilometers long rebounds. The magnitude of the event defies imagination - think the Toba Eruption, the Yellowstone disaster and a baker's dozen of Krakatoas packet together. It's not a remake of the Chicxulub Impact, not even by far, but that's precious small comfort. We'll still get the lava lake and nuclear winter, but not just yet.
The whiplash effect triggers the San Andreas fault in such a way that you can wave California goodbye, but that's still nothing - the crust at that point is probably several hundred meters below equilibrium. Ten meters are more than enough for a seven or eight Richter quake.
A slice of the Pacific Ocean is displaced by those several hundred meters, not instantly but in a matter of hours, and starts traveling towards Japan and the Chinese and Australian coasts at a speed of about 800 kilometer per hour (depends on water depth). People more than two miles off the coast will probably survive.
Upon arrival, shoaling brakes the wave to about 80-100 kmph, but it still strikes like the fist of Poseidon, and boy is Poseidon pissed off. We lose all the Pacific islands, so much of New Zealand and Philippines that it isn't funny, a good chunk of Japan (that actually depends), most cities on the Chinese coast. The quantity of water involved is at least one order of magnitude above that of a tsunami, because a chunk of the West Coast of the US has now lifted above equilibrium.
Several others tsunamis of more or less the same magnitude follow.
Before departing for parts unknown, Klark Cent is heard whispering "Oh sh*t".