WASHINGTON — The Corporation for Public Broadcasting, a cornerstone of American culture for three generations, announced Friday it would take steps toward its own closure after being defunded by Congress — marking the end of a nearly six-decade era in which it fueled the production of renowned educational programming, cultural content and even emergency alerts. The demise of the corporation, known as CPB, is a direct result of President Donald Trump’s targeting of public media, which he has repeatedly said is spreading political and cultural views antithetical to those the United ...