My husband has dementia, can I ethically put him into a nursing home and move to the United States?
If you’re planning to move to the United States now it is you who have dementia not your husband.
Or perhaps you are not very intelligent.
Are you very wealthy because if you’re not the plan is inconceivable.
Are you going to live with someone very rich in the United States who is in desperate need of a new wife? Be very careful.
How my heart sings 
Can I move somewhere that is free of income inequity, stupidity, sexism, endless care giving obligations, cruelty and racism? I wish there was such a place. I’d move there and bring my family. Of course, that would mean bringing the endless tasks with me. It’s tough to live with dementia. It’s tough to be forgotten by someone you love. It’s tough to lose your connection. My sympathies.