For companies that have mostly used external suppliers, isn’t supply chain risk the suppliers’ responsibility?

Your company - you choose suppliers - big part of your responsibility

Company cannot wash off its responsibility. The business is not suppliers' it is ours. It is our responsibility to link the risk as far as possible with the supplier.  The Rest of which is our part of the game.

It's company's responsibility. That's why all the research is getting done before appointing any supplier. 

A supply chain may not be quite as dynamic or complex as capital markets, but when it comes to managing supply chain risk the challenge is, arguably, can be as formidable as managing risk for instruments such as mortgage-backed securities or credit default swaps. Perhaps that is because of all the moving parts that there are in a supply chain, which we define as a network of companies that cooperate to convert ideas into goods or services for their customers.

I agree with colleagues answers.

when Japan was hit by a tsunami in2011, most companies thought their supply chains were safe because they had multiple suppliers as backups. As it turned out, many of those suppliers relied on the same secondary suppliers, causing the entire supply pyramid to collapse.

AGREED WITH MISS IRINA CHEPEL.................

No, it is your obligation to check out your vendors ... that they have the ability to provide the goods to you.

A vendor can only take the order and fill it in time to the best of their ability, but can not foresee a strike ... not all vendors will eat the cost of higher priced merchandiser... however they must inform you and source other manufacturers, but you are the one which is agreeing to a higher price ...  or cancel the order 

Risk is an important part of the company's work

(Risk Management Department)

You have to pay attention

That should be

one benefit of supply chain is you are not totally dependent on one external supplier.