trump saying americans can be imprison el savador

The full costs of course being borne by the USA.....?

Would it even be legal?

Britain abolished "Penal Transportation" as the law rather than modern American prolixity called it, in the 1860s; but perhaps it is still legal in the USA....

As it is, or at least is still used, in the Russian Federation though there, to remote places still within Russian territory.

President Donald Trump on Monday reiterated that he'd like to send U.S. citizens who commit violent crimes to prison in El Salvador, telling that country's president, Nayib Bukele, that he'd “have to build five more places” to hold the potential new arrivals.

And you can lose all your rights because he has hinted that he will pull the same stunt that was done with Gitmo. State that your rights and the authority of US courts hold no power on foreign soil.

Great way to create not only a penal colony but a human rights black hole.

Increasing our exports

Dangerous Criminals yes.