The NSA routinely receives – or intercepts – routers, servers, and other computer network devices being exported from the US before they are delivered to the international customers.
"Contrived computer chips found their way into
Soviet military equipment, flawed turbines were installed on a gas pipeline, and defective plans disrupted the output of chemical plants and a tractor factory."
~ https://www.cia.gov/library/center-for-the-study-of-intellig...
Well being inside the USA doesn't protect you from receiving modified equipment, it has been reported that the NSA will, for certain "Persons of interest", intercept hardware in transit and compromise it.
So not only routers.