Washington warned to not get involved in foreign matters and to follow the policy of isolationism, to avoid European powers because America wasn't really strong and big at that time. So involving in European matters could result in controlling the USA however they wanted and getting the USA involved in European conflicts. USA didn't follow Washington's advice and later on got involved in WWI and WWII. If they didn't they could've focused on improving domestic matters rather than wasting money in warfare.
Examples of self governance during the period of salutary neglect would be the implementation of town meetings and the general assembly known as the House of Burgesses.
