Tiny, invisible spies and saboteurs?
He warned that components sold in the US, whether networking equipment or smartphones, should be manufactured stateside or in allied countries.
If you accept (as you should) that where dangerous adversaries are concerned, you must address capabilities rather than intentions, this statement is absolutely correct. Even leaving soft- and firmware aside, it is simply too easy to hide nano-nasties in hardware, and incredibly difficult to find those intelligently crafted to lurk dormant until some set of conditions exist. The Internet of Shite means that many erstwhile dumb devices are now net-connected, often for no good reason, and it's entirely plausible that a seemingly gormless appliance, supposedly intended to monitor your stock of chilled dairy, is (a) much smarter than it appears and (b) relaying everything heard and seen in your kitchen to Beijing. Or Maryland.
And when you consider the fantastic complexity of, say, PC mobo design—no individual has a perfect knowledge of every component and connection in one of these things today, nor ever will—there are so many places and methods of sneaking in a hardware nasty no bigger than a blob of solder that it would be brave indeed to claim that one you hadn't personally designed and built was guaranteed free of infection. When you're talking national security like nuclear systems, utilities, military logistics, political data, banking and high-tech research, 'brave' becomes 'foolhardy'.
Pretty soon every country and alliance that can self-source its high tech will do so.
If you're still wondering why, ask yourself a question. Supposing your adversary is an authoritarian, secretive regime with complete control over its citizens, scientists and corporations; that it employs supremely gifted and capable biologists; expends huge resources on research in this area; and that it has developed advanced technology to support these efforts: would you allow it to contribute to your national blood bank?