Here's an example of the effect of tariffs to an ecommerce business. I have a shipment waiting to go to the US. An order costing a bit more than the deminimis $800 threshold for customs so duty/tariffs might be due. We might have got a customs clearance fee of £16 from the courier but as nothing on it incurs duty, probably not. With the tariffs, here is the calculation:
item1, origin: GB, special tariff is 10% (£0.62)
item2, origin: GB, special tariff is 10% (£1.87)
item3, origin: GB, special tariff is 10% (£3.75)
item4, origin: CN, special tariff is 54% (£9.03)
item5, origin: GB, special tariff is 10% (£11.67)
item6, origin: GB, special tariff is 10% (£16.66)
items7, origin: EU, special tariff is 20% (£41.67)
Then there is the clearance fee on top. Just over £100 total has been added to this customer's order.
Most of our orders are not this big so the overall effect would not have been that much. Unfortunately, we sell quite a few Chinese made products and the real sucker punch is the new deminimis cancellation for Chinese goods. Any order for one of those will now cost 50% more plus the clearance fee. This will pretty much wipe out all of those orders, I suspect.
I sympathise with Americans who are annoyed that they've been paying for our defence (and consequently our heavily generous benefits system) for decades. Also the feeling that something urgent should be done about the problems of large scale immigration and drugs coming across their borders. Generally speaking, the media and politicians do over-hype stuff. Remember the whole Brexit fearmonger thing ('it's a train crash', we were going to 'fall off a cliff into the abyss' the day after etc'). We soldier on; it caused short term pain but overall only a minor market shift. However, the orange ignoramus living in his own feedback bubble has got this badly wrong. Anyone who thinks these tariffs will not have much effect and things will settle down after a while are living in cuckoo land. Hence the market reaction. The only question is whether it will be a recesssion or a depression.
Still, as with all problems, there are also opportunities and the UK has been given a significant edge.