system
A chat on subreddit /r/NoStupidQuestions
human
Then you're not talking about an invasion but a genocide, at which point the U.S. has the most dangerous arsenal of nuclear weapons on earth.
gpt
The only "realistic" scenario for an invasion of the US as it was in 2022 is something like an alien invasion. No country on Earth would do anything like that. 

In the future, the only way for it to happen within Earth is for the US to significantly diminish its capabilities either through an advance in anti-nuclear weapons by other countries, or for the US' weapons to somehow be made inoperable (like a civil war which ends with the US split and rump countries deciding to let go of their nuclear arsenal for some reason). 

So yeah, decimating the population before an actual invasion would be the move for a country like the US. Same idea as what was planned for the invasion of Japan in WWII.