If you are colour blind, I'm afraid I can't comment, but if its myopia, I have a personal anecdote for you. Bearing in mind it's from 2018 so might have changed.
The Canadian Class 1 has - on paper - stricter requirements than the British. I assume from your mention of an optometrist that your medical problem is eyesight.
From personal experience back in 2018 the Canadians are a lot more lenient than the CAA and I was able to get a Class 1 with a note from an optometrist explaining that my retinas were not at danger of detaching (cost of note: $100 and a short eye examination.)
How old are you?
If you are younger than 35, you can go to Canada on a three-year working holiday visa, and with the right moves, get your Permanent Residency (the younger and higher-educated you are, the better.) You might be eligible for
PR right now - check. The earlier you apply the better.
On a working holiday you can work for whoever you like, although it's hard to get a "proper" job like flying without
PR. Once you've got
PR, you will be better eligible for "proper" jobs. I met at least a couple of flying instructors and CPL candidates who had got
PR and then landed their positions.
This will be easier immigration-wise than the USA.
Disclaimer: I'm (still) not a pilot - due to cost - and I don't have my
PR (possibly my biggest regret in life, although it is one I am trying to rectify.)
HOWEVER: DON'T LET TRYING TO BECOME A PILOT CONSUME YOUR LIFE. I did, and I forgot to live mine. I don't entirely regret it but I would be in a much better position now if I hadn't. The advice by others to seek out another career and fly for fun is not without merit and you should consider it very carefully.