They wanted a united nation. A bunch of individual state currencies would make trading, taxing and fining within the nation a pain.
People in the south used slaves because their economy was focussed on things like cash crops (tobacco, cotton, etc.) These crops required a lot of work so farmers and plantation owners could not do it by themselves. So by using enslave persons they could harvest more crops, sell more, make more money, and in return boost the southern economy.
In addition to patronage, merchant families during the Renaissance began to "spread the ideas" of the Renaissance, but promoting the artwork was that based primarily in Florence outside of the region.
Um what is this supposed to be