Does USA as a nation have any power at all over any action the sitting
Sure. That's what elections are for. If you are displeased with the president (and are an American citizen eligible to vote) then you can vote for someone else.
On top of that, the House and Senate can work together to impeach a president.
Finally, the courts can rule that certain actions the president took broke the law. For example, Trump's earlier immigration execution actions were struck down by court action. Similarly some parts of Obamacare were struck down by the Supreme Court.
Does the sitting president require approval of any instance or body in
the US Government before signing executive orders that are acts of
The president does not have the power to declare war. The constitution grants Congress the power to declare war. I presume you are asking because of the recent Syria action. The legality of that is currently being debated and I'm not going to spend time on it here. All I'll say is that the president doesn't have the power to declare a new war, only Congress does.
In violation of approval, what are the punitive measures by law that
this body can take?
The president is still a citizen of America. All existing laws still apply to him. If he shoots someone he'll still be charged with murder. There are various abuse of office statues throughout the US Code, but they have never been applied to a president. Realistically what would happen is impeachment (see: Nixon).
The Attorney General can pass law that prevents the actions of the
sitting president, but obviously the president will appoint the AG
that will comply with his wishes.
The Attorney General can not pass any laws whatsoever. Your point has no bearing on the rest of your question.
Congress. Obviously the party in power will have 50% (or near) of
complying members that will have great chances of obstructing any
intervention with the sitting president's wishes.
Again, Congress can impeach the president. As for party loyalty, keep in mind that only works when the wind is blowing in the right direction. This is what happened to Nixon. His illicit actions became so damaging to his own party that they eventually decided that it wasn't worth defending him anymore. That is when it was really over for Nixon.