What was the cause of extreme cold in USA in January and February 2019 ?

The correct choice is: “Weakening of Polar Vortex”

The polar vortex is a large area of low pressure and very cold air that circulates around the Arctic. When it is strong it keeps the cold air locked near the pole. A sudden stratospheric warming at the end of 2018 weakened and split the vortex, so lobes of Arctic air spilled far south into the US Midwest in late January 2019, bringing record lows (below −40 °C in places).

A strengthening vortex would have kept the cold air in the Arctic; Antarctica and ozone depletion have nothing to do with a North American cold wave.