If you think you need to pay more to US, you had better

to file to US and the state where you work, especially you hope to work in US in the future. All taxes including fed, state, social security and medcare tax are the tax you have paid in US, then take away the amount to US from the tax you need to pay to Canada.

it looks your situation is defferent from him/er who just woked in US for 6 months and has already back to Canada and no plan back to US.