US' self-harming protectionism

If it is understandable that the United States would want to prohibit government departments from purchasing high-tech products from other countries for security reasons, such concerns do not justify the US authorities placing a ban on Chinese smartphones in the US market.

Since the US government has long proclaimed itself to be the guardian of the market economy and fair competition, why does it choose to obstruct the access of foreign goods to the US market? In so doing, the US sends an unambiguous signal that it prioritizes the protection of the interests of a handful of groups while sacrificing market economic principles and the right of its consumers to know and to choose.

US President Donald Trump has time and again emphasized fair trade. However, recent cases indicate that for the US fair trade means taking all that benefits for itself.