The American R is not tapped or trilled: the tongue never touches the roof of the mouth. In bird and word it becomes a vowel of its own, /ɝ/.
Pull your tongue back and bunch it up without touching anything, round your lips a little, and keep the sound smooth. No tap, no roll.
20% of 79,851 scored /r/ sounds in the SayWhat app were scored red, from at least 6,896 learners.