American Opportunity Carbon Fee Act of 201 8 This bill amends the Internal Revenue Code to impose fees on: (1) fossil fuel products producing carbon dioxide emissions, including coal, petroleum products, and natural gas; (2) fluorinated greenhouse gases; (3) emissions of any greenhouse gas from any greenhouse gas emissions source; and (4) associated emissions (attributable to venting, flaring, and leakage across the supply chain). The bill directs the Department of the Treasury to: establish, implement, and report on a program to identify all major source categories of associated emissions and collect data on associated emissions from the coal, petroleum products, and natural gas supply chains; make specified adjustments to the new fees for importers and exporters of energy-intensive manufactured goods; make a specified payment each calendar year to certain Social Security beneficiaries, veterans, and disabled individuals; make cost mitigation grants to states to assist low-income and rural households and provide job training and worker transition assistance; and establish a website to make regular disclosures concerning revenue, tax savings, and benefits attributable to this bill. The bill also allows a new carbon fee offset tax credit for the lesser of: 6.2% of earned income, or $800.