This is a brief overview, not tax advice — cross-border rules are detailed and change periodically. The links below go to official sources for anyone who wants to go further.

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• U.S. tax law treats most foreign (non-U.S.) mutual funds and ETFs as passive foreign investment companies, or PFICs — this sweeps in nearly all Canadian-listed funds, regardless of what they hold.

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• PFIC tax treatment is punitive, and IRS Form 8621 is generally required for each PFIC held. This is a big reason U.S.-based investors overwhelmingly stick to U.S.-listed funds, even for international exposure.

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• If a U.S. person holds any account at a foreign financial institution and the combined value of all such accounts exceeds USD $10,000 at any point in the year, FinCEN Form 114 (“FBAR”) reporting is required, separate from the annual tax return.

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• Larger foreign holdings may also trigger IRS Form 8938 under FATCA. Both of these are disclosure requirements, not tax bills — they apply based on account balances, not on whether tax is owed.

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• A TFSA isn’t treated as tax-free by the IRS — income and gains inside it are generally taxable on a U.S. return each year.

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• An RRSP or RRIF is the exception: tax deferral on RRSP/RRIF growth generally carries over to the U.S. return under the Canada–U.S. tax treaty.

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Where to go deeper

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Instructions for Form 8621 (PFIC reporting) — IRS  — the official IRS instructions covering who must file and why

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Report of Foreign Bank and Financial Accounts (FBAR) — IRS  — the official IRS page on FBAR filing thresholds and requirements