The average tax rate for a single person making 250K in Sunnyvale is 32.93% [1]

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