both
yes There are actually 2 types of national guards. There is the Air National Guard which is part of the Air Force and the Army National Guard which is part of the Army. Then there is the State Guard which certain states have and work closely with the army national guard.
The differences are pretty widespread. The Regular Army (active Army) is a fully federal, full time force. The National Guard, on the other hand, has a state role, as well as a federal role, and is composed of part-time soldiers. Since the National Guard serves in the role of the state militia, they are permitted to be used in law enforcement activities when activated at state level, whereas the Regular Army cannot be used for domestic law enforcement duties unless the Insurrection Act is invoked.
The Army National Guard and Air National Guard do work together. Although, most missions are different and require that they work on different tasks. You will most definitely see Army and Air National Guard working together on a big project.
state governments
big mac
The federal government has become the dominant player in federal state relations. This is to assist the states to work cohesively with the national government and ensure that resources are distributed in an equitable manner.
cooperative federalism
They didn't work because they gave too much power to the state government and not enought to the the federal(national government).
You're probably thinking of the National Guard, but state militias still exist, although not every state maintains one. They're known as a State Guard or State Defence Force, and they tend to be oriented more towards first response and search-and-rescue work.
Any person living in one state can work in another state.
It would be difficult. It is up to you to attend drills with your unit. You may request to be ING (inactive national guard) by notifying the unit and see if it will be granted.
It doesn't quite work that way. The States and their people ARE the government, and they have allowed the Federal government to do a very few things like regulate sales of items between and among the States, provide a military to protect all of the States, and to mint money.