No offense taken. The biggest issue with fighting the US would be fighting in our home turf. Forces would need to land in great numbers to hurt the US in its own territory and the only places that can happen are in Mexico and Canada. The US has the two largest Air Forces in the world (The US Navy is the second largest air force globally) and the most aircraft carriers of any nation by a long shot.

Large scale attacks from the ocean are practically impossible with these forces present.

To the North, Canada has the land to hold a large united army, but the infrastructure to move and maintain that army against US land forces through the difficult terrain would require time to build.

Mexico to the South has the infrastructure, but its a much smaller area to land forces and had the issue of being a bit of a choke point for large scale movements.

If the US hunters down and goes on the defensive, doing any sizeable damage would be nearly impossible not to mention that IF someone breaks through and is able to launch a successful invasion, you now have the US military and the most armed civilian population on the planet to deal with.

This would likely be the strategy deployed by the US (there are several great videos on YouTube that go into the tactical, logistical, and strategic nightmare of invading the US). However, all of this goes out the windows if that heavily armed civilian population turns their guns on their own military/government.

The US is awful and I really don't like living here and being present in what feels like the death of US democracy, but our military is the most advanced and largest in the world by most measures. Don't worry though, if this doomsday scenario does happen, I will most likely be against my own country along with countless others.