I am an American citizen married to a Canadian. What if I return to the States for benefits under my former vet husband,who is deceased?

Are you planning to leave your current husband? Or are you planning for his demise? I have no idea how it works in the US for returning citizens. Did you file US taxes while living in Canada? If not then you will have another issue to resolve before moving back.

As a resident (not citizen) of Canada, you should have access to the provincial healthcare in your province as long as you are legally in Canada. You will get your hospital and doctors visits fully covered and should be eligible for some prescription coverage if you need it.

Were you divorced from your veteran spouse or Widowed? And if divorced, how long were you married?

If you are a US citizen and do not have enough work credits of your own to receive Part A (hospitalization ), you can actually pay for it. You need to contact the Social Security office to see what your SS and Medicare status would be in US.
There is more to it than I’ve written here but all roads lead back to contacting SS for your personal status in regards to obtaining insurance.
Since your family is in the US, I can certainly understand you wanting to be near them.
I hope your husband is getting the care he needs and you can find your perfect home for the future. 

I think there is a penalty for taking Medicare late. Part B is higher I think. You say former husband so I am assuming you r divorced? If so you Can't collect from him. Widowed may be a different thing but remarrying may keep u from benefits. I would think Canada would be ur better choice with socialized medicine and cheaper pharmaceuticals.

I think you lose all rights to benefits from a former spouse if you remarry. Do you have rights to any Canadian benefits?
Unless you are independently wealthy which I assume you are not there will also be the problem of enrolling in Medicare.
Do you have family in the US who could check this out for you?
The cost of living is probably cheaper in the US but healthcare I would expect to cost more. You may not feel it is any better once you have experienced it. The care of the elderly especially those reling on Medicare is often substandard. not all Drs accept Medicare patients and waits for specialist appointments can be very long, 3 months is not unusual.
Get all your facts together before you make a decision

Wow, FF, I had no idea. Great answer.

Francine, I came across this information from Military.Com. military.com/paycheck-chronicles/2015/04/30/survivor-benefit-plan-and-remarriage

This was written in 2015, and with the current U.S. Administration you would need to check to see if this still exist or has been changed.

I wouldn't think so. But this is a better question for an elder law attorney in the state you want to live.