How to pronounce The CAR R-Vowel /ɑr/ in American English

Drop your jaw significantly for the open AH shape, then lift the tongue back and up while bringing the lip corners in for the R. The trick is making it feel like one continuous glide rather than two separate sounds. Tongue tip stays behind the bottom teeth for the vowel, then either the middle of the tongue lifts toward the roof of your mouth (bunched R) or the tip curls backward and up (retroflex R).

British English (and Boston, parts of New York) drop the R entirely after a vowel, leaving just the open AH. Casual American English fully pronounces the R, and the R-coloring takes over the back half of the syllable. If you just pronounce the open AH vowel without adding the tongue and lip movement for the R, you'll sound British. The R has to follow through: lips flare, tongue lifts back and up, and the heavy R catches the tail of the vowel.

You're likely separating the vowel from the R instead of blending them. Speakers from languages with trilled or tapped R sounds often pronounce a clean AH, stop, and then tap for the R. American English wants a lazy glide. Let the tongue float back and up while the lips flare; the vowel and R fuse into one continuous shape. Your tongue should never tap or touch the roof of your mouth.