The contribution of slave labor to the US economy was minimal.
Almost all the wealth created by slave labor was created in the South.
Almost all of that was destroyed in the War Between the States (Civil War).
It is almost certain the U.S. destroyed more wealth in the Civil War than was contributed by slave labor over the entire history of the United States.
Something a lot of people do not understand is that the US Government was funded by tariffs for decades prior to the Civil War. Tariffs were taxes placed on imports.
Imports were paid for by exports.
The South produced the vast bulk of US exports in the decades leading up to the Civil War. In 1860, the South produced between 73% and 85% of the total US export value for the nation.
This means the South was responsible for creating 73% to 85% of all US taxes funding the government.
Washington DC mostly spent the money in the North. Very little of it was spent in the South. The Big city liberals of that era were financing all sorts of government subsidized train systems, often that went no where.
Same then as now. Big city liberals loved them some big spending government programs that would produce trains to nowhere.