I was in California for this summer - I paid about the same for a cell service there as I do here...
All numbers in USD.
For a quick comparison of "premium" cell providers, an unlimited (15gb before throttling) verizon wireless line is $70 per month [0]. A comparable Canadian plan for Bell is $56 per month for 10gb before throttling, or $71 per month for 20 gb before throttling.
Most people don't pay that much in reality, because of group discounts and so on, but that applies in both cases.
The story is similar if we look at budget cell phone providers. Google Fi (US) provides unlimited talk and text for $20gb/month with data for $10gb/month. Freedom mobile (Canada) doesn't provide as much flexibility, and you have to select your amount of data up front, but for any amount of data it's cheaper. E.g. for 2gb it's $30/month instead of $40. [2]
[0] https://www.verizonwireless.com/plans/ - change the number of lines to 1, this is 15gb data before throttling per their faq https://www.verizonwireless.com/support/verizon-plan-unlimit...
[1] Remember to convert CAD to USD https://www.bell.ca/Mobility/Cell_phone_plans/Unlimited-plan...
[2] Click on "Freedom Plans" here, remember to convert CAD to USD https://www.freedommobile.ca/en-CA/plans