washington collapse islamic state self-proclaimed caliphate diminish militant group ability inspire attack western target via internet u.s. national security officials tell senators wednesday sunni muslim extremist group build external operations past two years claim link least 20 attack western interest since january say lora shiao act director intelligence national counterterrorism center unfortunately see isis loss territory translate correspond reduction inability inspire attack tell u.s. senate committee isis capacity reach sympathizers around world robust social media capability unprecedented give group access large number hves shiao say use government acronym homegrown violent extremists u.s.-led coalition fight islamic state estimate tuesday few 3,000 fighters belong hardline sunni militant group remain iraq syria declare caliphate 2014. isis drive raqqa syrian city call capital october prompt president donald trump say end isis caliphate sight yet elimination physical caliphate mark end isis global terrorist organizations say mark mitchell act assistant defense secretary special operations/low-intensity conflict isis lose territory become reliant virtual connections say continue inspire stray dog attack vulnerable people senators question security officials u.s. efforts fight online recruitment potential extremists new caliphate cyberspace say ron johnson republican chairman senate homeland security governmental affairs committee experts describe evolve threat include isis ability adapt narrative territorial losses portray struggle long-term process internet primary tool radicalization group successful isis draw people message say nikki floris deputy assistant director counterterrorism federal bureau investigation possible reference trump use twitter democratic senator kamala harris ask floris fbi examine role social media post videos government officials affect online recruitment tactics use isis answer u.s. officials warn isis new caliphate cyberspace