Yes you can add a bank account from a US based bank to your PayPal account, even if you are Canadian. I set one up back in 2001.
However, it has to be from a US based bank, not a US$ denominated account from a Canadian bank.
In Profile, under add a bank account, you need to select "other bank"
Then change Canada to USA
Then PayPal advises:
Add a Bank Account in the United States
The safety and security of your bank account information is protected by PayPal. We protect against unauthorized withdrawals from your bank account to your PayPal account. Plus, we will notify you by email whenever you deposit or withdraw funds from this bank account using PayPal.
Enter your name exactly as it appears on your bank account statement. If the names do not match exactly, the transfer will fail and a return fee will be charged. Learn more
"it is already linked to my US Paypal account,"
If your US bank account is already linked to your PayPal account, it will not let you add it to a second PayPal account if you use the same account number.
Why would anyone need two PayPal account?
Each PayPal account can be used with eight different email addresses - meaning one could have eight eBay User IDs all linked to the same PayPal account, with as many currencies as you want (I use Cdn$, US$, € and £ )..
"I also have different Paypal accounts for my different websites"
That is a lot of bookkeeping work!
I have sold on five different venues (including three eBay accounts) and had my own website (prior to retirement) all on the same PayPal account.
