Americans have grown smug. They've never seen war at home. Not truly.
Outside of the Revolutionary War and the War of 1812, no adversary in war has ever had the military ability to significantly impact the contiguous US, and while that may well happen one day, it isn't gonna be Iran of 2024 who changes that run.
It's also not likely that any country will have that ability near term outside of a preemptive nuclear strike, and a country set on doing that has to be able to counter or accept the US response, which I don't anticipate any country doing in the near future.
More-realistic concerns might be terrorism or economic pressure.
Not the primary image, though I'd bet that you can stick an image inline in the body in spoiler text. You couldn't get a thumbnail then, but I think that might be undesirable anyway if you're wanting to hide the image by default.
EDIT:
test
Looks like it.