War crimes trials for all former presidents and high administration officials. Then I'd expose intelligence agency crimes, close overseas bases, and reorient foreign policy towards peaceful cooperation with all nations. Then there'd be corruption and incompetence trials for most politicians across the country. Dissolve the two establishment political parties.

Institute medicare for all, legalize marijuana, pardon all non-violent drug offenders, a massive public health campaign to curb drug addiction, transition to carbon-free electricity, massive research into fusion energy and carbon sequestration, shorten the work week, universal childcare, mandatory paid leave, parental leave, a universal jobs guarantee, rewrite labor laws to heavily favor unions and unionization, bring the financial sector under state control, ban private equity, nationalize natural resources, free universal pre-k education, college, and apprenticeships, build publicly-owned fiber networks like in Chattanooga, build massive public housing projects for people at all income levels, a housing-first policy to end homelessness, force cities and suburbs to adopt car-reduction planning strategies and density increases, build bike lanes and separated bike roads, build public transit everywhere, build a high speed rail network, police and prosecutorial reform (including harsh penalties and prosecutions for any said official who abuses their power), encourage the formation of cooperatives over traditional corporations, force traditional corporations to allow workers to elect members to the board of directors and adopt employee-ownership plans, break up big tech monopolies, break up monopolies in all sectors of the the economy, and adopt the metric system.

After implementing these policies, I'd call some kind of congress together and have them just run everything. Elections would be publicly financed, with no private donations, and limits on political campaigning.