A CME like the one in 1859 (Carrington Flare) directly hitting the Earth would cause the upper layer of the troposphere to grow hundreds of kilometers.
That could potentially catch LEOs into the atmosphere, where they would immediately start to heat up and be dragged down into a fiery crash.
We're all Americans here. It's really okay to use standard English measurements. In fact, most of us prefer it that way.
We're not totally Eurofied yet.