Which of those other 27 are big enough in the US to be worthy of mention?

How about Xiaomi? Wikipedia says that as of 2017 they're the world's 5th largest smartphone company. I don't know how popular their products are in the US, but I have at least heard of them before (which is more than I can say for ZTE).

I’d venture to say 98% of the US population couldn’t tell you if Xiaomi was a tech company or a Chinese food dish.

Considering that the name literally means little rice, they wouldn't be necessarily wrong. (at least it isn't 小蜜, which has a different meaning...)

That's true of Huawei and ZTE too, and yet the government thought it was worth saying don't buy their phones, so I'm not sure what your point is.

My point is that Xiaomi phones are not popular in the US, at all. Xiaomi had zero official distribution in the US up until recently when they started selling directly on amazon. ZTE and Hauwei phones have been sold through official distribution channels for a while. ZTE phones are given away or nearly given away for free to every cricket wireless customer.

I am more aware of Xiaomi than Hauwei. ZTEs were around, but those are garbage phones. I know that Xiaomi makes phones, smart bands and a smart tv. I literally had no idea what Hauwei was making until I looked up right now.

Huawei made one of the Nexus phones.

FYI, Xiaomi is very popular in India, because they offer perceived good value for the cost.

Xiaomi now has the largest market share amongst phone manufacturers in India.

Xiaomi has almost zero presence in the US market, you can't get their phones here unless you go via a grey market importer.

Or Amazon.com...

The witnesses only answered the question in front of them. Sen. Cotton only asked about ZTE, Huawei, China Telecom, and China Unicom, so Director Wray responded only about ZTE and Huawei. This is standard practice when testifying in front of an oversight committee.