2) Cause massive Economic Disruption in the U.S. most likely leading to the collapse of the country into a depression as it is unable to sustain it's current system based on the resources currently within the United States being incapable of fulfilling the needs of Americans?
It might help economically as it could very well bring back manufacturing jobs to the US. Any given state can only use so many fast food restaurants!
It takes but a basic understanding of Economics to know that America does not have the resources alone and within itself to be self-sustaining. Quite simply, we cannot produce everything within our own borders that we need. Unless reverting back to 1860 is on your mind. Other countries have resources that we need, but that we do not have a supply of. Thus, we have to trade that which we need with them for whatever goods it is they need. It is as simple as that. You can't simply close the borders to trade and expect the U.S. to be able to independently provide for 300 million people without outside trade.
We don't need to produce EVERYTHING. but it would be nice if returned to producing some things and stopped exporting jobs that we could use here in the states.
There is a lot of open space between "closing the borders" and free trade with countries who are our enemies. We are rapidly approaching a situation where every machine screw used in the US will be manufactured in China. Consider the "massive economic disruption" we will suffer if we have to go to war with China.
For our own safety, we need to work on being more self-sufficient.