How hard is it for an American citizen to become a Canadian citizen? Or get dual citizenship?

If you have a canadian ancestor you can get in fairly quickly. If you have 10 million to invest you can buy your way in. Other than that, it’s not easy. I think they have quotas from countries.

You are a nurse, so you shouldn’t have too much problem with a skilled visa like any first world country.

As for other people, it depends on your skills and if a person or company will sponsor your visa.

Is dual citizenship even a thing anymore? I thought they stopped doing that but I could be wrong. (Edit: I’m probably wrong.)

Here is a list of programs you may be able to take advantage of to come to Canada. https://ircc.canada.ca/explore-programs/index.asp Not sure if it’ll help, but it’s worth a try.

There is also bill C-3, which allows people who’ve had ancestors here claim citizenship. https://immigration.ca/claiming-canadian-citizenship-by-descent-under-canadas-new-citizenship-act-bill-c-3/ (Not a gov’t site, but has a decent breakdown of C-3)

Good luck! I hope you find something that works for your bro.