Shipments under $800 that are sent through the international postal network will be “subject to a duty rate of either 30% of their value or $25 per item (increasing to $50 per item after June 1, 2025).”
That’s the end of cheap treats from AliExpress, Shein and Temu, I guess. 
McMaster is super expensive too, it really isn’t built for normal people to buy from them. Until there is a 400-500% tariff this wont do anything besides making stuff more expensive.