Subject: Re: MI for non-Americans
I would assume that you still have the choice of filing a tax return in the U.S. and recovering the excess withholding. N'est ce pas? Maybe it's not worth the hassle to you.

Nope.
First, what a horrible hassle that would be. I'm neither a US citizen nor "US Person" for tax rules.
And second, there would be no benefit, as far as I could see. To get a credit on the tax paid, I would presumably have to declare the related income (or class of income) as taxable in the US, something I'm understandably not keen on doing.

Heck, if I were filing US tax returns most of my banks and brokers would never talk to me again.

Jim