Can an american pick out a Canadian when out abroad ?

Usually I can, yes. 

Certain words: 
About 
Schedule 

Sometimes just a general accent. 
Or what they talk about. 

There are some "tells", so yes.

Not in my experience, no.

Difficult for me to answer as I am neither. I am British. I cannot distinguish Americans from Canadians. However, I would have expected Americans and Canadians would be able to make the distinctions.

Some can, and some can't.  It is the same as Canadians detecting an American.  I usually can, but not always.  I have a good ear for accents though, which not everyone has.

On a trip to England, I was surprised at how many could tell I was Canadian, not American just from my speech.  Of course, many couldn't, but an amazing number of people could.

I can usually tell if someone is Canadian. There are differences and they're pretty subtle.

There is something called the "Canadian Rising". For example: 
 "I like ice cream." Becomes 
"Oy lyok ioys cream." I trying go give a phonetic spelling. Of 'I' becoming the sound 'oy', as in bOY.

Best I can do.

It really depends on an individual's ability to detect nuances.  Some Canadian regions have very distinctive accents; for example, most Canadians can tell if someone is from Newfoundland or Nova Scotia.  That being said there are certain pronunciations of letters and words that are different from American pronunciations.  Canadians say "zed" while Americans say "zee"; Canadians say "Leftenant" , Americans say "Lootenant"