The ACA is currently being challenged in the Supreme Court, with oral arguments scheduled Nov. 10, one week after national election day. The Kaiser Family Foundation's policy paper explains that if the Supreme Court affirms the Fifth Circuit's decision and tosses out the entire ACA (on the basis of a specious severability argument), the result will be the rescission of federal permission to expand eligibility and the unavailability of federal funds to subsidize each state's expansion. (So far, 39 states have accepted the federal offer. Texas, with the most uninsured and highest uninsured rate in the country, has not.)
The result of overturning the ACA will be a Hobson's choice for expansion states: Either cut back the eligibility cutoff to the pre-ACA level: "income eligibility limits for parents were very low—typically just 64% of poverty, equating to less than $14,000 a year for a family of three in current dollars." Most states cannot self-fund the expansion, especially in light of the COVID-19-era hit to their budgets (on both the revenue and expenditure sides).
Add this effect to the loss of the ACA's broad range of insurance underwriting reforms --protection for patients with pre-existing conditions, the ability to keep a child on her parents' health insurance plan up to age 26, abolition of life-time and annual caps on coverage, elimination of the ability to rescind a policy simply because the insured has started submitting claims, etc. -- and the devastation will be all too real for tens of millions of Americans.