Royal mail in the UK had to flat stop accepting parcels to the USA for several days just to have time to put in place a stopgap measure.

I now have to pay an extra £1.50 "administration charge" for every gift I send to a friend in the USA, despite gifts under $100 still being exempt.

Australia Post has stopped on-shipping (I don't know the technical term) parcels from other countries to the US, and also stopped accepting parcels valued over $150 bound for the US.