The math on this doesn't math.
You're old enough for a routine colonoscopy, yet pay $200/month for a platinum plan?
I'm not old enough for a routine colonoscopy and pay more than $200/month for a bronze.
The only way that happens is if you're getting a significant subsidy. Which, based on your later statement about your income taxes, doesn't add up. You can't simultaneously be in a high enough bracket to pay that much in income tax and a low enough one to get health insurance subsidies.
Moving on from that, your statement about it being cheaper than what you would pay in taxes is completely unfounded and incorrect. We spend more than 2x per capita on healthcare than any of the "national health system" countries.
Cancer patients are at the top of the list in every healthcare system. US, Canada, UK, France, Norway, Denmark.. you name it. Your time to treatment wouldn't have been any different in any of them.
Without clear information about income, it's hard to know where you'd land, but I reasonably suspect that cutting the cost in half (which every other nation is able to do), even if you're in the top bracket, it would end up equal or lesser.
Plus, you wouldn't have any deductibles.
You'd be money ahead if we got rid of the rent seeking/leach insurance companies.