CRA indicates that Canadian residents who are subject to the U.S. transitional tax generally will not be entitled to a foreign tax credit

A U.S. citizen resident in Canada holds a controlling interest in a U.K. company. The U.S. imposes its one time transition tax on the "earnings and profits" of the U.K. company held at certain dates in 2017. CRA indicated that the individual would not be entitled to a foreign tax credit, given that the income in question was Subpart F income that did not qualify as income under the ITA, so that typically the formula in s. 126 would not work.

Neal Armstrong. Summary of 29 May 2018 STEP Roundtable, Q.12 under s. 126(1).