I worked in the US and had to file a US tax return. When filing my Canadian return, can I claim fees related to a US tax accountant as a work expense?

If you are Self-Employed with an unincorporated business, you can include the expenses in the Self-Employment (T2125 - Statement of Business or Professional Activities) section of your return (Income> Self-Employment). There is a space there especially for “Legal, accounting, and other professional fees”.

If you are employed and you have a T2200 form from your employer, you can claim your Employment Expenses like this: https://turbotax.community.intuit.ca/replies/2647650