You do not have to close a US bank account but there can be issues in accessing funds as you can see from previous answers. An easy solution is to open an account with the US bank owned by your Canadian bank. I have my accounts with RBC Royal Bank in Canada. I arranged to have them open an account with RBC Bank USA. I can access my accounts in Canada and the USA through one online banking sign on
They provided me with a debit card and a Visa card. When I am in the USA or purchasing from a US website I use my US$ Visa card. They give me a preferential exchange rate if I need to exchange currency.
Because we visit the USA I have found this has saved me money.
The only trouble I had was when I paid with a cheque once. The lady saw my Canadian address and she accused me of giving her a foreign cheque. I pointed to the address of the Bank and told her that I was pretty sure Georgia was in the USA unless they had seceded again.
