Huawei makes some great stuff, lots of anti-competition against them.
TP-LINK is a good cheapy brand, surprised they aren't being targeted too.
First, because this is not about consumer equipment. Consumer equipment like cell phones or home routers is just peanuts. This is about infrastructure equipment.
Second, because Huawei has an extremely bad reputation. When you have a bad reputation suddenly everything looks suspicious. E.g. the link to the PLA. No one would probably ask about that if they had an otherwise spotless reputation.
I have friends working in the telecommunication industry. They all claim the well known case of Huawei copying Cisco routers, hardware, firmware, even copying the documentation 1:1, was just the tip of the iceberg. They all had stories about friendly Chinese interns dutifully doing their work and attentively listening. And then disappearing the minute their contract was up. Month later the design appeared copied in China.
This is how Huawei gained their bad reputation, by copying. I don't think the US wants to protect US industries. There isn't much to protect. Non of the really big players is a pure US company. Looking at the runner-ups, Ericsson is Swedish. Alcatel-Lucent is a French/American mix (and the US government helping the French? I doubt it). Nokia Siemens Networks is Finnish/German. And these are the big players, not Motorola (split, parts now with Google), Nortel (Canadian and bankrupt), not even Cisco is playing in the Huawei league.