NO if the tax was withheld against the Canadian Company then that is US tax withholding against any tax owed to US BY the Canadian Company.
See This from IRS:
Any person required to withhold tax is a withholding agent. A withholding agent may be an individual
, trust, estate, partnership
, corporation, nominee (under section 1446), government
agency, association, or tax-exempt
foundation, whether domestic or foreign.Liability
for tax. As a withholding agent, you are personally liable for any tax required to be withheld. If you fail to withhold and the foreign payee fails to satisfy its U.S. tax liability
, then both you and the foreign person are liable for tax, as well as interest and any applicable penalties.
The applicable tax will be collected only once. If the foreign person satisfies its U.S. tax liability, you are not liable for the tax but remain liable for any interest and penalties for failure to withhold.
Si, if as you say they do not owe this tax to the US they will file a Foreign Corporation tax return:
... to get a refund