American Sign Language has more in common with French than with British Sign Language

Despite the US and UK sharing a spoken language, ASL and BSL are mutually unintelligible — they even fingerspell differently, one-handed versus two-handed. ASL instead descends largely from French Sign Language, brought to America in the 1810s by educator Laurent Clerc, making it structurally closer to LSF than to the sign language used just across the Atlantic in England.

— Standard linguistic and historical accounts, American Sign Language — Language family and origins