"In trials conducted by the General Lighthouse Authorities of UK and Ireland, a 1.5W radio jammer was able to knock out GPS signals over a range of 30 kilometers. However, to do the same to the Loran system, you'd need a 40ft tower — and around 25kW of juice to power it."

https://www.engadget.com/2013-01-21-uk-eloran-navigation-sys...

Well certainly, no one thing is impervious. But if you have GPS, LORAN, VORs, NDBs, astronavigation, etc. you have many more options at your disposal and present a much more complex attack target.

Not so simple. For one the distances to the transmitter are much smaller, for another the amount of power available to the transmitters is pretty much whatever you want to hook it up to, whereas GPS satellites are on a pretty strict power budget. On the reception side the power levels are many orders of magnitude apart.

Not really. It uses 2MHz band, with the wavelength of around 160m.

This means that it's easy to receive via a ferrite bar antenna but hard to transmit. You need an antenna of at least around 40m size for that to be efficient.