Pretty hard to misunderstand that.
A piece-meal approach to the invasion of our country isn't constitutional, and it isn't workable. It's a loony idea, frankly.
And, by the way, the states already have the legitimate power to protect themselves if the general government will not do so, as the Constitution requires. The right to self-defense is intrinsic.
In the case of invasion, the Constitution explicitly acknowledges that.
"The Privilege of the Writ of Habeas Corpus shall not be suspended, unless when in Cases of Rebellion or Invasion the public Safety may require it." - Article I, Section 8.
The Constitution is not a suicide pact. Never was, never will be.