Is the correct spelling travelling or traveling? I’ve seen both in common usage, but I can’t find an authoritative source that says one way or another.
Is this a difference between British spelling and American spelling?
There is no hard-and-fast rule that is universally applied, but in general, many and perhaps most writers of American English use just one single L there.
Other varieties, including British, Irish, Australian, New Zealand, South African, and (usually (but not always)) Canadian, almost invariably use two Ls there.
I draw your attention to the first bullet point under “Doubled Consonants”.