You make yourself look mighty ignorant when you throw out nonsense like this:
"How about "Gun control policies are law and sovereign nations have every right to determine such laws."
Actually, sovereign nations DO have the right to make gun laws, just not America because our Constitution, 2nd Amendment, forbids it.
As for immigration, Article I, Section 8 has long been interpreted as giving Congress that role. The fourth clause of the section says Congress shall have the power to establish a uniform "Rule of Naturalization," as in determining who can legally be in the country.
What happens if you 'open border' yourself to China, Saudi Arabia or even Mexico? Why don't you try it and tell us how it went?
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy.