What if the enemy gives aid & comfort to you instead? Is that treason?
Is it covered by a different crime?
This is not treason on the part of the recipient, although it could involve receipt of a bribe, or failure to register as a foreign agent, if it were in exchange for the performance or expected performance of some official act or a fee for service. Motives and the identity of the donor would matter.
Also, "enemy" is a term of art in the law of war and the law of treason in the United States. Basically, it means someone who is a national of a country which the U.S. is in a declared war. Other than members of some some terrorist groups (including ISIS), and possibly citizens of North Korea, I do not believe that anyone else in the world counts as an "enemy" at this time for legal purposes.
The U.S. Constitution in Article 1, Section 9, Clause 8 does specify that it is improper to receive "emoluments" from a foreign power. It says:
[N]o Person holding any Office of Profit or Trust under them [i.e.,
the United States], shall, without the Consent of the Congress, accept
of any present, Emolument, Office, or Title, of any kind whatever,
from any King, Prince, or foreign State.
In other words, no federal government official may receive any gift or title from a foreign government or monarch. State Department protocol ratified by Congress mandates that when gift from a foreign government or monarch is received by a U.S. government official because international etiquette requires it, that it be turned over to the United States government to become federal government property as soon as it is reasonably practical to do so without offending the donor, since the purpose is to prevent a government official from personally benefitting from his or her office.
I suspect that it is a crime to receive an emolement without turning it over to the U.S. if you are a federal official whether or not an "enemy" provided it. If I have time I will look up the chapter and verse.