Are active duty and national guard units interchangeable? Troops?

I do not feel that they are not interchangeable in whole. The NG and Reserves are a great augmentation to the Active force. If they were interchangeable, then the NG and Reserve would not have to go through a train up before they deploy. Unlike the Active component that trains all the time for their missions and are ready to deploy at any given moment, the NG/Reserve do need some time to fine tune their skills.

While I feel we reserves are sometimes at a disadvantage because of the nature of our service, to deride the reserve components entirely would ludicracy. Others have mentioned good points on this so I’ll just add one other.

Coming from the medical field, you will find some of your most experienced and best educated medics and professionals in the reserves. Our civilian experience often gives us a significant knowledge and skill edge. Likewise, I am sure MPs with civilian law enforcement experience are a force multiplier as reserve/NG service members that aren’t quite matched in AD. There are things each component will be better at simply based on training and experience availability.

Since the GF1- NG troops have received better training and issue. Many NG units have replaced AD units around the world- MFO (Sinai), Bosnia, etc. With that being said I shudder to think of the learning curve trying to swap a AD company in an AD BN for a NG company just before deployment.

No they're not interchangeable. Give a guardsmen time and dedication then maybe, but for a good majority I've met a bunch of chewed up NG' that need training for proficiency at their MOS.

First, soldiers are soldiers. That said, the Army places many of the combat service support functions in the RA and many of the Combat Support functions in the NG. An example, close 70% of medical assets are in the RC. What drives these decisions?, funding. It cost less.

The two components are much closer than they used to be.

For OCONUS operations and functionality Regular Army (RA) and Army National Guard (ARNG) units should be interchangeable given equivalent equipment and support.
Within CONUS, RA and ARNG units are not interchangeable. The ARNG units are legally authorized to operate within CONUS is support of the respective Governor's directives frequently in responsible to natural or man-made disasters and threats or NORTHCOM requirements.
Background" Although my military career was spent in Regular Army and USAR units, I spent roughly one year as an on-site consultant supporting the Logistics Directorate at ARNG HQs in Arlington, VA after I demobilized in 2004.

In theory, they're supposed to be interchangeable. After a brief spin-up, ARNG units should be deployment ready. Reality, however, is another story. From what I remember - it's pretty hit or miss.

My experience would say active, Guard, and Reserve are close to being the same. Back in the 80s that not so true. Today Reserve and Guard are so busy they are much better than they were after Vietnam era.

As a career reserve component soldier, I am a little biased but my challenge is this -
Please name a time a reserve component unit was given a task they could not accomplish but an active duty unit could?