It is absolutely horrible, and I'm beyond furious about it. According to the renovation contracts, that cladding was Celotex RS5000. The insulating material in that product is polyisocyanurate foam. The US Material Safety Data Sheet on that warns that it is quite flammable and that the smoke is toxic. Butane is among the chemical components of the stuff, so you can imagine how hot it can burn. In the US it is illegal to use it on a high-rise; you can only put it on a building less than 4 stories tall.
What a lot of Americans are not realizing about this story is that Grenfell Tower is public housing, though some of the flats were privately owned (it's complicated how, so I won't go into that here.) Some of the private owners were renting out their flats, at an average rent of $2500/month, so the building is not the sort of environment that Americans tend to think of when they think "public housing project", at least not now. Kensington & Chelsea is the wealthiest borough in London these days. Though this particular area was once a near-slum, it has almost completely gentrified now. This housing estate is one of the few remaining semi-affordable options for working-class Londoners. Many of the tenants in this building were elderly &/or disabled, as they get first dibs on available Council flats.
The RBKC Council uses a private management firm, which is very handsomely paid for their work -- or lack of it. This 24-story building had ONE narrow staircase running down right through the center of the structure, one single-wide exit door (no additional fire exits), no sprinklers, and apparently, no working fire alarm system. It also apparently had a very wonky electrical system, as there have been reports filed for several years now showing major electrical surges that have caused appliances to actually burst into flame. Even without the plastic cladding, that building was horribly unsafe for a fire scenario, and the Council was very aware of it. In addition, there are no streets that directly abut the building, and only one very narrow dead-end street that leads into and out of the estate. The complex (there are several buildings) is set up as a walkable green space, with lots of sidewalks that have bollards placed at intervals. The fire crews responded within 6 minutes, but the trucks could not get close enough to really be much use. In this photo, the tower is the red square, and the purple line is the only road in, the one that the fire trucks all had to try to use.