The answer is because their power had grown to point where they decided it was time to run a test of public opinion. Their test seemed to have succeeded, which is a green light for them to push further. As we grow more and more complacent to their dominance, they'll begin to use cruder and cruder methods on more and more important figures, until we end up in a dystopian society without even realizing it.
What are you recommending? Or are you just focus-grouping a new Young Adult novel?
Speaking of focus-grouping...
Constitutional Amendment: The US may only exercise force of any kind if granted a specific 4-year mission to do so by popular vote. The proposal is given thusly: "Shall the US be allowed to deploy troops and weapons to Trinidad and Tobago, Monaco, and Liechtenstein from 2021 to 2025; and shall the US increase taxes by 0.04%?" No further context may be provided in the voting booth, although the government may make a public case leading up to the election. The US may ask to extend the mission (refreshing the 4-year duration) once per year in November, but the initial vote to establish the mission can be an emergency vote. The measure is tied to mandatory "war tax." Non-votes are considered "no" votes. The non-voting population also automatically votes "no."
The USA always has permission to operate defensively within National waters and its own territories, including within 3 miles of a US border (horizon distance), but may not change its territorial claims without declaring a mission (no deciding that Mexico is basically US territory). All animals, personnel, and devices that are equipped with weaponry, as well as all projectiles and any energy effects, are included. A national guard platoon carrying fruit baskets doesn't count; a dog with a gun in its mouth counts. A bullet, laser, or catapult projectile can strike anywhere within the specified areas, but not outside the area, by this provision. All other rules of war apply.
The war tax is an additional tax assessed after all other taxes. For every 1000 square miles of active mission area, Americans must pay 0.02% higher taxes. For example, we're current at war in around 500,000 square miles. Americans would pay 10% more in taxes. I am not a tax lawyer, so those numbers might change, but this feature exists for the specific reason of preventing the workaround of asking Americans to vote for war against "everywhere" every couple of years. (This may be modified to be based on the projected population in the combat area, so that declaring war on Antarctica is cheaper than on Hawaii, but that is for later negotiations)
Failure to comply with this amendment constitutes treason on the part of the commanding officer(s) responsible.
This way, we will never again be in a situation where we wake up involved in a new war, police action, "advisory role," etc. I think this should do it, though guys. I saved America!