What is the greatest threat to the United States and how might we combat it or prepare for it?

Ourselves and apathy.

Externally it is China, without a doubt, economically, militarily and also from an espionage perspective.

Internally it is our government chipping away and liberty and the apathy of the American people and their willingness to live in a nanny state because they think it will make them happy. The nanny state may sound good to some but once it gets rooted it will show its teeth.

SGT Joseph Gunderson Russia, China, North Korea, Iran, and other countries are all possible threats. Keeping a strong combat ready military is essential. Our country is deeply divided over many issues, and this is great news to our enemies.

Partisan politics and the current division. Destroying us from within.

Americans...stop procreating?

greatest threat to the United States is Identity Politics - where what makes us different is more important then what makes us the same - You see it everyday - idiotic cultural appropriation call outs and shaming, (over a dress worn to a prom), the slow and methodical removal and demonization of all things masculine (no more boy scouts, yet see the outcry if a boy wants to join the girl scouts), the stupid terms of "mansplaining" and "manspreading", how the left have redefined the definitions of racism and sexism in order to further their narratives and agendas, ( cant be racist to white people, cant be sexist to men), how we now have to carefully watch how we say something for fear it might offend someone who will then go on social media in order to destroy you, how groups like Antifa, who have shown and utilized violence to further political goals, are glamorized by our media outlets, and how the Media themselves are destroying not only their credibility, but our society.

We've all heard the house on the hill metaphor -- well, the foundations are crumbling

The People's Commie Paradise and the Hermit Kingdom, the only way to deal with them is to create a SEATo analogous to NATO, and just contain them both, till they get ow out of their Commie cultural immaturity phases, just as wit the Soviet Union...I can envision no other way, honest....

Drugs. There are so many people trying to find an escape for whatever reason. They resort to substance abuse. Not the occasional drink or 4 after a tough week at work. I mean the person who does felony levels of IV methamphetamine or ice or heroin. Law Enforcement is really spinning their wheels keeping up with the new drugs hitting the streets and how to deal with them. We can't really focus on international problems when dealing with nationwide drug issues here.

The dumbing down of society....reject banality. Read a book

Lack of youth entering into skilled and licensed trades....put down the iPhone and decide carefully whether a college education is the best fit for you.

Lack of manufacturing and heavy industry in the United States. The Arsenal of Democracy is anemic.