There are several key sources that can help us understand what the first president of the United States, who died in 1799, would have thought of the next four decades of US history. The first is his own words, especially as contained in his farewell address. The second is the succeeding events and policies on which he took a stance, often early in his career.
In his published Farewell Address, Washington advocated unity and some centralization. He warned against the formation of political parties, seeing them as divisive. The founding of the Democratic Party and Whig Party in the 1820s–1830s would likely have distressed him.
Washington greatly favored westward expansion and private land acquisition (his own holdings were vast). It would be interesting to speculate about his views on the US territorial growth from the 1803 Louisiana Purchase and the westward push with the 1830s Indian removal and the Trail of Tears under Jackson.