Short answer: Generally no. Under the Affordable Care Act, an insurer cannot retroactively cancel (rescind) your coverage just because you made an honest mistake on your application. Rescission is allowed only if you committed fraud or intentionally misrepresented an important fact, and the insurer must give you advance notice first.
Before the ACA, insurers sometimes rescinded a policy, canceling it back to its start date, after a member filed a large claim, citing an error on the original application. The law now prohibits that. Under the Affordable Care Act, rescission is illegal except in cases of fraud or intentional misrepresentation of material fact.
Federal rules say a plan or issuer must not rescind coverage unless the person performed an act, practice, or omission that constitutes fraud, or made an intentional misrepresentation of material fact. Even then, the insurer must give you at least 30 days’ advance written notice so you can appeal or find other coverage. An ordinary cancellation for non-payment of premiums is different and is not a rescission.