I want to turn on the way-back machine for a moment, because a question was asked in a previous post, but now it is buried so many pages back, and now I can't find it.
The question was along the lines of "how can the President make laws without having to deal with Congress. Many European PMs cannot get things done because they can't work it through the legislature.
Are presidential decrees omnipotent in the USA?
What we don't understand here in Europe are your presidential decrees.
All parliaments are struggling for majorities and Trump can really decide everything he doesn't like on his own?
Wait, I did find it. I just had to go back 14 pages.
I'm going to make the assumption this is a serious question, and not simply trolling.
The short answer is "no".
The longer answer is this:
I cannot stress enough that a Congress is NOT a Parliament.
What you are calling a Presidential Decree is in fact an executive order. Understand the three branches: The Legislature makes the laws, the Executive executes the laws, and the Judicial is the "umpire", ensuring both sides color within the lines.
An Executive Order is how the boss directs the Executive Branch to execute the laws. What he is really doing is directing priorities.
In a simpler world, these orders would be simply that. But two salient things have compounded this.
The first is the Legislative Branch has been a bit lazy. They will create an Agency, or Directorate, or whatever, and then allow that agency to create regulations within its charter. Of course, that Agency is within the executive branch (executing the charter), and so the Executive Orders play a large part in creating the regulations because the Legislature did not fully do its job.
The second issue is there are now simply too many laws, and many are contradictory. So then the Executive, in determining priorities, can dictate enforcing one law and not the other.
In the first example, take some of the Orders cancelling Agencies or Directorates (i.e. USAID, Department of Education, et al.). If the guy responsible for ensuring the laws be faithfully executed decides that some of the regulations created by those agencies are invalid, not useful, or contra to policy, then in good faith, he can instruct that Agency to stop doing those things. That's his job. He's not overstepping the majority in Congress, he's determining how the agencies in his portfolio should function. If he oversteps, that's where the Legislature gets involved. The Legislature can solve this by not being so lazy.
Similarly, US Border Patrol is responsible for (not surprisingly) patrolling the border. So the President gets to direct how they do that, within the confines of the law. Directing the deportation of people who have broken immigration laws is clearly within his purview. If Congress believes those immigration laws should be changed, they may do so.
In the second case, the order cancelling DEI programs is a good example. One regulation/policy created DEI programs. At the same time, there are laws directing equal opportunity. The two are clearly in tension, and the Executive is directing his staff to enforce the law, not the policies.
One can argue all day long which someone believes should be the priority... but one man is elected to make that determination.
Unlike a Prime Minister, it's not his job to rally the party. He does not direct the legislature. President Obama once said he expected Congress to enable his agenda. He had it exactly backwards. The President is supposed to execute Congress' agenda. Things have gone pear shaped because we have forgotten that simple concept as outlined in the Constitution.
The blame for that goes back a long way. Personally, I blame Woodrow Wilson. And FDR was no help at all.
Finally, we have the subject of tariffs. Now, the power to levy taxes and tariffs are clearly within the legislative branch. So how can the President do this? Remember that bit about Congress being lazy and delegating their responsibilities?
They gave the President the ability to determine tariffs when they passed several laws, including the Trade Expansion Act of 1962, the Trade Act of 1974, and the International Emergency Economic Powers Act of 1977.
Congress can fix this by repealing these laws. But they would have to have a veto proof majority to do that, because no President is going to willingly give up these authorities. Why would he?
Hope this helps.