News flash: Random late-night postings on Truth Social do not constitute "bilateral trade agreements"
And any trade agreement has to be ratified by Congress and the equivalent institution in the other country. None of that has happened.
That's mostly correct, but IMO it's worth understanding the nuances.
The "ratified by Congress" phrase indicates that you're thinking about the Constitutional treaty approval process, which requires a 2/3 vote of the Senate (no involvement of the House).
But that's not the only type of treaty the US enters into, and in fact it's the least common kind. Another important kind is the "Congressional-executive" treaty, in which the executive negotiates the terms and then takes it to Congress to pass as an ordinary bill: majority vote of both houses plus presidential signature. This makes it federal law exactly the same as if it went through the Senate "advice and consent" process.
The third kind is the "sole-executive" treaty, in which the executive negotiates and enacts the treaty without any congressional participation. This perfectly constitutional as long as the content of the agreement consists of things that the executive branch already has the power to do, either because the required power is granted to the executive branch by the Constitution or because Congress has passed legislation that delegates the necessary power. The most common sort of sole-executive treaty is a "Status Of Forces Agreement" (SOFA) which the president signs with countries that are hosting US military forces. SOFAs are about how the military will act in those other countries and the president, as Commander-in-Chief, has the authority to issue orders.
In the case of trade agreements, Congress has delegated some trade agreement power to the president, so some trade agreements can be enacted as sole-executive agreements, depending on the content, though it's generally better to make them one of the other kind because what one president can do on his own, another can undo.
As for Trump's trade agreements, if the US side of the agreement is just about tariff rates, and if the president has the authority to set tariffs (a power SCOTUS just reduced but did not take away), then they could conceivably be enacted as sole-executive treaties. What has to happen on the other side varies, of course.
What's really interesting is if the US side of the agreement was to not enact tariffs that SCOTUS just said the president can't enact anyway. In that case, the other countries maybe allowed themselves to be rolled, because SCOTUS ruling does a lot to ensure that the US follows those agreements... but only because the US couldn't have broken them without congressional action anyway.
Time and again, people are learnng the hard way that making deals with Trump is a bad idea. Appearing to make deals with Trump, however, is a great idea. It's particularly effective to promise to do something in the future that you have no intention of doing and which Trump will forget about.