why did several regiments march on philadelphia after the war ended

The Continental Army had not gotten paid in months.  These people were working men and farmers who had signed up for the war in order to protect their homes and way of life.  Many had not gotten paid or were underpaid when the war was underway.  Now that the war ended, the former soldiers demanded payment.  The states were unable to come up with the debt, and even if they were, there was the question...

The Continental Army had not gotten paid in months.  These people were working men and farmers who had signed up for the war in order to protect their homes and way of life.  Many had not gotten paid or were underpaid when the war was underway.  Now that the war ended, the former soldiers demanded payment.  The states were unable to come up with the debt, and even if they were, there was the question of which states would pay for which soldiers.  It was almost like when a large group of people split a check at a restaurant--New York questioned why it had to pay South Carolina's war debt when New York had already paid it's part of the bill.  Even when the soldiers were getting paid, the Continental dollar was worthless due to inflation; there was a popular saying where something that was worthless was called "not worth a continental."  Something Americans take for granted today is that the American system of government was inevitable, but not really.  What the Founders were creating was novel in the history of the world and often revolutions had many counterrevolutions.  The regiments marched on Philadelphia in order to force the national government to pay them.  Ultimately, this led to the formation of the Constitution where the federal government would take on the states' revolutionary war debt.  The soldiers were ultimately paid in land in the West, which was one of the main assets of the new nation.