I read an opinion piece that speculated the disconnect between the Ukrainians and the US/NATO re the imminence of Russian invasion is because the Ukrainians have been at low level war with the Russians since 2014 when the Russians grabbed the Crimea. The Ukrainians are accustomed to Russian troops on their doorstep.
I also watched an interview yesterday with the Ukrainian ambassador to the US. She made the point that the Russians, with their bullying behavior, are trying to rattle, trying to panic, the Ukrainians. Remaining calm and downplaying the invasion risk is the Ukrainian way of resisting this pressure.