Worshiped. Whenever I type that word, I instinctively add in an extra P, and then delete it when I see the squiggly red line.
As with whitetho’s ‘canceled’ upthread, my British dictionary spells it ‘worshipped’; I have the idea that American English has a tendency to ‘rationalise’ certain types of words - ‘traveled’ as opposed to ‘travelled’ too, perhaps? - which might explain why they can look a bit off.
Definitely
I always have to look at it twice, I’ve gotten so used to people spelling it definately
Auxiliary. I was sure for the longest time that there was an ‘h’ in there.
Sacrilege.
Minuscule.
Restaurateur. People want very, very badly to put an “n” in there, but there just isn’t one.
“Awry.” It’s gotta be either spelled wrong or pronounced wrong.
spelled. 
I know, they both go, but I have been corrected sooo many times when I used spelt, I just couldnt let that one pass. And I didnt say a thing about the quotation marks, you’ll notice.
Is Canada part of the U.S. now? Actually, to your whole point I say piffle. That’s right, piffle! There are two major systems of English spellings … British and American. Saying it’s American vs. everyone else is disingenuous. Save that kind of talk for the metric system!
In as much as English spelling follows rules at all, there is a rule that trailing consonants are doubled in certain conjugations when the word is one syllable. American spelling follows that more strictly than British. Still, “cancelled” is about as common here as “canceled”.
Privilege
Atheist
Necessary. I struggle with the c’s and s’s.
I always have to be careful around ‘elevator’.
Also the ‘Philippines’.
mmm
That’s the one I always get wrong.
Inconcievable! That’s definetly rediculous.
Supersede.
It was years (and the use of spell check) before I realized it needed that second “s” rather than a “c”.
Idiosyncrasy.
Embarrass, embarrassment - why 2 r’s? Looks weird and I always use only one and have to fix it.
Athy, athier, athiest. Right?
Embarrassed is my most frequently misspelt 
word.
Maintenance
Cesarean-- I always want to put an extra e in ther
Judgment
Hypocrite