How does it make the immigration problem a nightmare. There would still be the same border control regulations on the highway, I assume.
You are thinking of "only" the highway. The highway is just one symptom of the NAU.
When thinking of the "highway" - if you just want to focus on that... and ignore everything else, then you need ask questions such as "safety" - who will control that corridor and will all trucks traveling that road need to follow the 'same' safety policy. If so, then 'that' safety policy will be an Umbrella for the three countries.
1. So, now we have a safety advisory council for all three countries. Now, because they are on "our" roads - what takes precedence? This 'new' safety policy or an existing one? Then, in this case - which one takes precendence?
2. Now that we have safety to concern ourselves with, what about "trade". What are the new trade policies? These trade laws, like the EU, will supercede American laws.
3. The obvious next step is - if you are 'TRADING' to such a degree - you are inweaving trade, safety - and because of "scary terrorists", now military - you would probably want a single currency - else, there would be too much fluctuation in invididual markets between countries.. - with such a trade agreement...THUS, the Amero.
So, now we have a trade, safety and currency that NOW is beyond America's sovereignty....
Then what?
Little by little this comes about... and this is ALL down without American citizens consent. Corrupt governors in Texas and elsewhere are allowing this to be built. Now, 'private companies' are pushing forward with the funding. Who are these "private companies" - who are they affiliated with?
Alot of nefarious things are coming our way.