Why would President George Washington warn the country to remain neutral, avoid debt, avoid sectionalism, and avoid political parties?

Because there were bigger, stronger, older nations that would

have loved to get their hands on that rich territory that the United

States covered ... France, England, Spain, etc. Washington knew

that the young USA could only survive as a nation if the people

remained united, and all those things ... taking sides in international

conflict (not remaining neutral), national debt, sectionalism (north

against south, east against west, old states against new states),

political parties (Whigs against Tories, Republicans against

Democrats), are things that could set groups of the people

against each other.