Tariff for used item from Canada to US

I am at a loss to understand this.  I am in the US.  For many years I have been buying electronic (and other) merchandise from foreign countries. Among these 2 cartridges, a DAC, connectors.  They have come mostly from Asia, but also from Canada and Europe.  About 5 months ago I bought a renderer/digital bridge from a private party in Canada listed on the Canadian Audiomart.  Today I received electric cable from Hong Kong. 

I have never had to pay a tariff.  Never.

I have sold to Canadian buyers and it has always been my understanding that Canadians have to pay tax, and brokerage fees unless they make arrangements, which are unavoidable.

Thanks for your opinions. Others be careful buying from foreign countries  in the future.
Cheers

I believe the tariff could be exclusive to equipment of Chinese manufacture due to the previous U.S. administrations trade war policies.

I bought a streamer from Hong Kong last year and it was held until I paid a tariff.