> It's "practicing invading North Korea" in the same sense North Korea's missile tests are "practicing dropping nukes on America."

The context here is extremely important. All of this (the invasion exercises, the missile tests, the Korean War) have taken place in the Korean peninsula. None of it has threatened the US homeland in a meaningful way.

In addition, the exercises have been going on since 1997. That's a long time before any missile tests were conducted. If the DPRK (North Korea's name for its state) had been testing nukes from Cuba in 1997 I'd feel differently. But note that even dropping live bombs on other countries is something the US gets to do without starting a war because the US military is so powerful. Very few other countries operate that way and North Korea certainly isn't one of them.

I don't know if you're aware of it, but your framing is uncomfortably close to the North Korean diplomatic position, where it pretends that it's a matter to be settled between NK and the US, and any other countries are bystanders. Conspicuously absent is yet another country that will be directly affected by any conflict. Where do you propose the South Korean military conduct its joint military exercise to defend itself from North Korea? Texas?

(Of course, the official North Korean propaganda is that South Korea doesn't matter, because it's merely a colony of Imperialist America, to be liberated by our brave northern brothers. How nice of them.)

> the exercises have been going on since 1997.

North Korea has been caught developing nuclear weapons as early as 1992, which led to it threatening to withdraw from NPT in 1993. It's a shitty situation with decades of history, and you could easily find plenty of things to blame on both sides. But interpreting it as the US threatening to invade NK is a pretty biased take.