I am a Canadian CPA working in NYS. It's very easy to get an entry-level job with your CPA in NYC. For CPA firm openings, the best time is from September to February. Agents are not interested in the entry-levels and most of them do not have any idea about TN visa (even the big ones like Robert Half). Try New York Times if you are looking for NYC jobs. A lot of mid and small employers do not like to hire agents due to the cost considerations.
If you happen to be in Albany,NY , try to visit www.lcszcpa.com. The firm might have openings in this fall. And the bosses are great.
Good luck!