Starting tomorrow, the US Constitution goes out the window and instead, everyone just accepts that the entirety of the USA is one giant parliamentary democracy. The largely unwritten constitution of the UK is imported in lieu of what exists to facilitate rights protection and clarity of process.
No federalism/no states… it’s all one big government now. All US territories are carved up into electoral ridings in the same style as the UK. Elections for MPs start immediately. FPTP would be used.
How does it go down from there? What policies get enacted? Is the country better off or worse off? Speculate.