why is it not possible (on average) for the US to export the same amount of goods/services that we import?
It's possible. But it would mean the USA was no longer as wealthy a nation.
You currently take more from the world than you give back. The world accepts this, because the world likes US Dollars, and the only source of US Dollars is the USA. The USA has a literally inexhaustible supply of US Dollars, and can make as many as she wants at zero marginal cost.
Why ... would you
want to stop getting stuff in exchange for what (to your country) is available for no effort, and instead start only getting stuff in exchange for stuff your countrymen have to put in effort to obtain?
We should be producing what we consume and not printing the money to purchase what we import.
Why??