The average tax rate for a single person making 250K in Ontario is 39.80% [2]
But with the extra taxes you also get some better benefits like healthcare, cheaper education. Of course if your main goal is to save as much money as you can, then it probably better in the US because you earn more salary and USD converts better into other currencies.
[1] https://smartasset.com/taxes/income-taxes#I4RNWQ9WYm [2] https://simpletax.ca/calculator
Here's a detailed example (grep for "Average tax rate"): https://www.canada.ca/en/financial-consumer-agency/services/...
(Source: https://simpletax.ca/calculator)
You're immediately forgetting State taxes, Social Security, Medicare, and such. That 34% quickly becomes 44 to 50% depending on where you live.
Utter bullshit. Source: the many friends and family members who have been treated by the system.