Why is all tax paid being returned? I was a US/NY resident in Dec only from Canada. I indicated part residency in state tax part - no chance in fed part.

If you were in the US for only a month in 2018, you are a nonresident for tax purposes.

TurboTax does not support nonresident returns.

However we have a partnership with Sprintax offering a nonresident tax filing solution to our TurboTax customers.

Visit the TurboTax/Sprintax site for more info or to get started.

If you have already filed your return, you must amend your returns. You will need to wait until your returns are accepted and processed and you have received your refunds before you can amend your return.

If you have not filed your returns, you can clear your return and then go to the Sprintax site to prepare a nonresident return.

https://ttlc.intuit.com/replies/7276605

Please see the following for more information.   US Tax Guide for Aliens 

Publication 519

I am a resident even though it war only December. I have severe ties with Canada with no plans to return.

To determine your tax residency for the US, you must pass the substantial presence test.  It has nothing to do with whether or not you intend to return to your home country.  You must have passed the 183 day test.  You  must file a nonresident US tax return for 2018.

You will be considered a United States resident for tax purposes if you meet the substantial presence test for the calendar year. To meet this test, you must be physically present in the United States (U.S.) on at least:
1. 31 days during the current year, and
2. 183 days during the 3-year period that includes the current year and the 2 years immediately before that, counting:
• All the days you were present in the current year, and
• 1/3 of the days you were present in the first year before the current year, and
• 1/6 of the days you were present in the second year before the current year.

By the treaty, you become a US tax resident, and a Cdn non-resident the day you leave, not simply after spending the required days in US.