Bipartisan bill would block Trump from quitting NATO without Senate’s OK

We don't need no stinking bill. NATO is a treaty organization. Membership required Senate concurrence and quitting requires the same. No, this is just another attempt to denigrate President Trump in the eyes of voters. Yes, members of both parties fear his popularity because President Trump is neither Republican nor Democrat, no more than John McCain...

The President can unilaterally rescind a treaty the last time it was done was by President Carter in 1979. The lawsuit to stop the treaty rescission was dismissed w/o review by the Supreme Court. Most of the writing on this is pre-Trump but President's seem to routinely ignore international treaties they disagree with in every administration. The outright calling out and stating the US is rescinding is rare.

This is simply a Trump bluff for members to get up to 2% of defense spending.

I found this answer on https://politics.stackexchange.com/questions/2772/can-usa-exit-a-treaty-that-was-signed-and-ratified
Credit to User102008

It depends on in the context of what law.

Under international law: A treaty signed and ratified cannot be "exited" except as provided by the treaty. Some treaties expire after a certain amount of time or when a certain thing happens. Some treaties allow a state to withdraw from it, which may or may not require a certain notification time before the state is considered withdrawn. Some other treaties do not allow a state to leave at all once it joins.

If a state tries to "leave" a treaty other than as provided by the treaty, then the state is still bound by the treaty in the eyes of the international community, and any action by the state contrary to the terms of the treaty will still be viewed as a violation of the treaty.
Under U.S. law: A treaty's effects within U.S. law depends on the specific U.S. legal instrument that is used to implement the treaty. U.S. legal terminology differs from the international one and there are several different kinds of things an international "treaty" can be implemented as in the U.S.:

What is called in U.S. law as a "treaty", as described in Article II, section 2, clause 2 of the Constitution: The President signs it and it is ratified by two thirds of the Senate. (The House of Representatives is not involved.)
A "congressional-executive agreement": The President signs it and it is passed (or has already been passed) as regular legislation by Congress through the regular lawmaking process (passed by majority in both houses and signed by president).
A "sole executive agreement": The President signs it and Congress is not involved.
The first two types ("treaties" and "congressional-executive agreements") both have the effect of federal laws under U.S. legal theory. As such, any parts of it which conflict with the Constitution (as decided by U.S. federal courts) are void. Furthermore, as with any other federal law, Congress can repeal or amend it by simply passing a new law that conflicts with it through the normal lawmaking process (passed by majority in both houses and signed by president or a veto is overridden by two-thirds of both houses).

The third type ("sole executive agreement") has the effect of an executive order under U.S. legal theory. As such, it can only act in areas where the President himself has the legal authority to act. The current or a future president can repeal or amend it unilaterally at any time by issuing a new executive order. And Congress can repeal or override it at any time by passing a law that conflicts with it through the normal lawmaking process (passed by majority in both houses and signed by president or a veto is overridden by two-thirds of both houses).

Note that in all the above cases where a treaty is repealed or changed under U.S. law (e.g. courts declare it constitutional, or it is repealed or changed by Congress and/or the President), it does not change the obligations of the treaty on the U.S. in the eyes of international law. Under international law, the domestic institutions of a state (whether it be courts, Congress, constitution, etc.) are all part of that "state", which cannot unilaterally alter its own obligations under the treaty, except as provided by the treaty. So for example if a court declares a treaty provision unconstitutional, then under U.S. law that provision would be void, and the executive branch will have no choice but to abide by that, even if it means it will have to violate the terms of the treaty in the eyes of the international community.