Agreed that 1st yr FO pay at a US regional is measly (probably make more working full time at McDonalds), but check out this perspective that some CX pilots have provided me.
If accepted to the CPP, you'll undergo training at FTA for a period of approximately 13 months (unpaid). You're not officially on the CX payroll and will not have a seniority number till they offer you the SO position after completing training (regardless if you already hold a fATPL and that is if they do offer you the position). Then you'll join as a local pilot, without housing/education allowances. How much difference does this make? I don't have the payscales/allowances around, but I was told that a 2nd year DESO would be making more than a local FO (1st-5th years?)! True, you'll have a lower seniority number, but as a local SO that paycut might be worth reconsidering.
If flying shiny new jets is your thing, then it doesn't matter then. I think the experience gained at a 121 operation in the US would be great experience. Remember that 2nd year pay jumps up into the mid 20's USD (yeah, not much), and 3rd year should be in the 30's-40's. By the 3rd year, I would imagine that you might have an opportunity for command and the pay would be 50+. Apply to CX as a DEFO
If you're indeed a decent pilot, I wouldn't worry about exams/interviews with CX (now if you only have high school diploma, it might be a different situation).
There was another thread that CX was looking for instructors for 3.5yrs before joining as a DESO, now that would be a great opportunity. I don't think anybody has more information on it yet though...
Good luck with your decision and application.