Yes, most people in this situation liquidate them. Dual US / Canadian citizen here living in Canada.
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.
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.