How do Americans bring about radical decentralization?
There's lots of existing notions which make sense - return to sound money, scatter federal agencies around the USA and depopulate Washington DC, make states responsible for funding and adminstration of welfare and retirement programs. Greatly reduce the power of FBI over local police forces, etc...
Here's one simple, focused thing Conservatives can focus on: pass "Inverse Condemnation" laws, which used to be common in the USA before the 1960s (which were, of course, removed by progressives)
Under 5th Amendment takings laws, we all know that government can only take property under clear eminent domain declarations and with just compensation. As part of this, many states and cities once had laws declaring government LIABLE to private property owners for their failure to preserve civil order. If a riot occurs and your store is burned - government must pay. If a homeless camp in front of your home or store, and you lose revenue - government can be sued for monetary damages.
such laws were common in the USA prior to the 1960s. Truly make local government financially responsible to preserve public order.
There are many changes that could be made, but this would change the political landscape of blue cities immediately.