You must be joking. Just FYI, I'm not an American and nor am I a supporter of Trump. In the recent Democratic Primary debates a majority of candidates supported state-sponsored healthcare for 'undocumented' ( sic, the newspeak term ) immigrants. On a humanitarian level I support this. I would hate to think that a person in need of medical treatment would ever be denied essential treatment. On a financial level, this is ludicrous. When coupled with the democrat candidates' majority stance of supporting decriminalisation of illegal border-crossing, this would be analogous to directly paying American tax dollars overseas. You can't look at this issue on purely social terms, it is economic in nature. If there is no disincentive for illegally breaching a country's borders to obtain access to that country's welfare system, it will inevitably attract the immigration of indigent populations from other nations seeking welfare that their own country cannot or will not provide. How could it be any other way? We've already seen this to be true. The migrant caravan from South America is already proof of this.

When you mention that 'passport control came out of World War I'. This is incredibly disingenuous. The politics of pre-WWI Europe can not be compared to the modern day. You are talking about an era where ideas that would be considered radically nationalist were completely normal. You may have been able to cross borders, but your ability to integrate economically into a new country may have been limited. Not to mention the fact that the entire economic landscape of this point in history is not comparable to our current era. There was no globalism, global trade and global industry would have been extremely minimal compared to today.