我是加拿大人（有米国ETF，broker （TD）会把CG报给我和加国税务局在加拿大上税），刚又查了下面的米国有关条文：

https://www.investopedia.com/ask/answers/06/nonusresidenttax.asp#

Key Takeaways

• Tax implications for foreign investors depend on whether they're classified as resident aliens or nonresident aliens by the U.S. government.
• Resident aliens who hold a green card or satisfy resident rules are subject to the same tax rules as U.S. citizens.
• Nonresident aliens aren't subject to U.S. capital gains tax but capital gains taxes will be owed in their countries of origin.
• Certain nonresident aliens who are in the U.S. for more than 183 days are subject to capital gains taxes.
• Nonresident aliens are subject to a dividend tax rate of 30% on dividends paid by U.S. companies.