i think this would depend on who originally broadcast the material… r u taking news clips from cnn?? probs would have to clear w cnn/parent company… tbh i dont think ur proposals r too dissimilar to copyrighted music, someone still holds a copyright to that broadcast material, just different parties are at play.
where this may differ: who has the right to broadcast a particular event. say u went to the inauguration, recorded the audio of the poem on a personal recorder, its ur own recording so surely itd be okay to use as a sample??? but often broadcast companies will pay for the rights to broadcast an event, meaning if someone else records that event, that company will have the autonomy to decide when/how ur personal recording may be distributed. & usually by attending the event theres some terms that come w purchasing the ticket that will lay out recording/broadcast rights in the tos.
ianal so take w a grain of salt, but i did work in this industry for quite a while and specifically dealt w copyright claims from media companies. looking into how sports events are allowed to be recorded/shared/distributed may give u a firmer idea of how the actual legal logistics of broadcast copyright works. thats where it seems to be most active w this type of content in the us.
at the end of the day, just as w copyrighted music, i think it comes down to how litigious a copyright holder wants to be abt their copyrighted material, and how able they are to recognize your sample as being their copyrighted material.