democratic presidential front-runner hillary clinton say wednesday attack brussels kill 30 people late brutal reminder must do defeat islamic state militants include european union member countries address stanford university california clinton say unite state europe take hard look protocols airports soft sit outside security perimeters clinton also say much support european partner also share burden us clinton say would like see european countries invest defense security way germany obama administration urgent task stop flow foreign fighters middle east citizens france germany belgium unite kingdom european passports make easy cross syria return radicalize clinton say clinton say many european nations currently alert neighbor turn away suspect jihadist border citizen passport steal european union countries also need share traveler information readily clinton say actually easy unite state get flight manifest eu nations eu nations get neighbor thank agreement unite state negotiate secretary state clinton say additional step could take europe creation new unify european border coast guard strengthen external border continent unprecedented pressure refugees migrants clinton say clinton also praise past partnerships unite state europe call nato alliance north american european countries one best investments america make republican front-runner donald trump recent days say unite state rethink involvement decades-old alliance clinton also take aim trump along presidential rival u.s. senator ted cruz texas slam offensive inflammatory rhetoric demonize muslims include could partner fight terrorism clinton europe help u.s. combat terrorism