While you can keep a TFSA around you'll end up paying taxes on the gains back to the states as well you need to file additional paperwork come tax time. If your TFSA gains exceed the filing requirements it might still be worth keeping. Historically you needed to file a TFSA as a foreign trust however recently the IRS has deemed them a foreign disregarded entity which reduces the filing requirements thus making it cheaper.
In your situation you could open up a US based fund with that money and Canada won't care so that's likely your best option.
Lets say you are a 0.1%er who happens to live in canada. Invest everything on canadas terms, then move to the USA. receive foodstamps, welfare checks and the likes for XX years. Go back to canadian citizenship and cash out. Darn, looks like tax payers supported the ultra wealthy while they just got richer eh?
It has a $6,000 yearly contribution limit.
Canada, if anything, has an investment tax scheme which favours middle class investors. For someone making millions of dollars Capital gains tax is tied to your income tax bracket in Canada so it is very likely that you would end up paying higher taxes.
Canada also has a tax and income information sharing with the USA, so someone making big bucks in investments in Canada could not benefit from means tested programs in the US.
The scenario you proposed is entirely impossible.
I haven't looked into the exact details of Peter Thiel's IRA, but those have a contribution limit too, and look at all the press recently about him "abusing" [0] that.
[0] I can't claim to know enough of his specific situation and the exact regulations to have an opinion on whether that's a fair characterization.
My point is that he bought private stock, something that is privileged, so it's not entirely accurate to say that all people benefit from a roth IRA equally.
I personally don't think that the average person has the ability to take similar advantage, even though they both have the same limitations on paper.
> move to the USA. receive foodstamps, welfare checks and the likes for XX years
Does this seem like a good use of your time, as a 0.1%er? Collecting foodstamps?