During his appearance on October 8, 2020 on the Rush Limbaugh radio show, President Trump put Iran, and any other enemy state, on notice:

Iran knows that, and they've been put on notice: if you f--- around with us, if you do something bad to us, we are going to do things to you that have never been done before.

This may not be as diplomatic as the Monroe Doctrine, where President Monroe warned Europeans that any interference or further colonization in the Western Hemisphere would be viewed as a hostile act to the USA.  But President Trump was giving a clear warning about would happen to Iran.  If President Trump had been president instead of James Monroe, he would have said: "Stay the f--- out of the Western Hemisphere."

This is like President Trump warning North Korea early in his administration that North Korea had better get its act together or else.

This direct talk will undoubtedly upset the tender feelings of the Obama-Biden weaklings who believed in the Obama-Biden Doctrine to bow before the Middle East dictators, appease China, and apologize for American exceptionalism.  It will upset the Obama-Biden media that believe that the way to deal with Iran was to give them $150 billion plus several billion in cash, which Iran used to fund terrorism.

It is not the language that upsets the Obama-Biden types, but the blunt America First meaning.

While President Trump directed his message to Iran, I believe that the message was also directed to communist China that allowed the Wuhan virus to spread throughout the world when it knew its danger.  China knew in December 2019 of the danger but failed to notify the world and failed to stop travel in December from Wuhan to the world.

President Trump has repeatedly said China could have stopped the spread and suggested that the USA will have China pay for the damages:

We believe it could have been stopped at the source. It could have been stopped quickly and it wouldn't have spread all over the world.

President Trump will seek to make China pay, probably through tariffs and increased trade restrictions on China.

In plain, simple language that thug countries like Iran, North Korea, and China understand, President Trump reiterated the America First policy, which is in direct contrast to the Obama-Biden Doctrine of appeasement.