I believe the Defense Authorization Act of 2015 (not sue of date) specifically permit POTUS to use the military in defense of a[-our borders - invasion is not the same as migration. If those were the same, then there is nothing to stop any foreign power from sending its troops into the US since they could simply claim they are immigrants.
The author conflates invasion with immigration to garner sympathy and to rose public opinion against POTUS and use of the US military to protect the country from invasion and maintain the security of the US.
A handful of people crossing the border could be immigrants - 10,000 or more waving flags of other nations is an invasion, regardless of the women and children being used as shields (like Saddam did before Gulf 1).
Hizbollah is. It's fair to describe them as a foreign power as well as a terror group given their control of Lebanon and decades of actions as an Iranian proxy. Including in our hemisphere