First of all, I should say I am not a pro at this but I have poked around on the issue.

While FinCen does handle money issues, they are more involved with tracking crime and terrorism issues. U.S. Customs handles most commercial transactions. Their website has a FAQ you'll want to read:

https://help.cbp.gov/cgi-bin/customs...i=&p_topview=1

It seems to me that since you had not endorsed your bank's check made payable to you when you left the US, it fell outside the definition of negotiable instrument, and therefore outside the requirement to fill out the form or otherwise notify US authorities. Whether you had any required reporting to Canadian authorities, and whether those requirements were met (technically or constructively) by your handing the check to the Canadian border person for inspection, I don't know.

But that's not all-Individual US tax returns (Form 1040) ask whether you have had at any time during the year more than $10,000 in foriegn accounts, which term includes banks. If you did, you have to file Form TD F 90.22.1-See here:

http://www.irs.gov/newsroom/article/...218835,00.html

There's no tax due with the form but there's a tough penalty if you don't file it. And remember, it's $10,000 US so I imagine that even if you went with only $10,000, currency fluctuations may have throw you over that threshold for at least a short while.

As I said, I'm no expert. If you want to confirm this, I'd suggest calling the general help number at US Customs.