The same reason almost no one is ever charged with treason, given the plethora of other criminal charges available to anything that might remotely be similar to treason: Article III, Section 3 of the US Constitution: “Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort. No Person shall be convicted of Treason unless on the Testimony of two Witnesses to the same overt Act, or on Confession in open Court.”
Even where the first part (in which, it should be noted, the terms involved are interpreted very narrowly) is not problematic, the “two witnesses" rule, which is applied independently to each fact necessary to sustain the conviction, is usually quite difficult to overcome, so its usually vastly easier to get a conviction for something else.
It's not levying war against the United States. I don't know what the legal definition of Enemies is, but I would imagine it would involve a declaration of war.
The Korean war was never formally resolved, but the US hasn't declared war since WWII.
There's also no indication of adherence here.
Doing things that benefit a country and a leader that your government officically doesn't care for can be all shades of prohibited and illegal, but it's not treason.
No one has been convicted of treason since WWII. One person has been charged with treason, but they were remote-murdered by the US government before they were tried, and it's not at all clear that a conviction would have withstood appeal. Note that Congress did expressly pass a resolution in the Global War on Terror that can be construed as declaring war on terrorists; if anything short of outright declaration of war qualifies as a foreign entity as an "enemy" for the purposes of the treason declaration, that is it.
Eh, if your president and his stinky regime does it...
Brandeis wrote about how a lawbreaking government breeds contempt for the law and invites every man to be a lawbreaker by in 1928, but since then women have gained more rights: https://www.azquotes.com/quote/1062178
The same reason almost no one is ever charged with treason, given the plethora of other criminal charges available to anything that might remotely be similar to treason: Article III, Section 3 of the US Constitution: “Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort. No Person shall be convicted of Treason unless on the Testimony of two Witnesses to the same overt Act, or on Confession in open Court.”
Even where the first part (in which, it should be noted, the terms involved are interpreted very narrowly) is not problematic, the “two witnesses" rule, which is applied independently to each fact necessary to sustain the conviction, is usually quite difficult to overcome, so its usually vastly easier to get a conviction for something else.