There has been a lot of confusion here lately over what does and does not constitute terrorism, and in the way these labels are applied and used. Some people are of the opinion that only non-state actors can be considered terrorist groups, whereas others would argue that 'terrorism is as terrorism does'. The line is
further blurred, however, when states are taken to task for having terrorists within their borders or for (knowingly or unknowingly) doing business with them, allowing them to do business with others--just about anything, really. What is needed here is a clear definition of what is or isn't terrorism, followed by a clear policy implementation consistent with this definition.
Fortunately, the United States came up with a definition back in 2001:
the term "terrorism" means an activity that --
(i) involves a violent act or an act dangerous to human life, property, or infrastructure; and
(ii) appears to be intended --
(A) to intimidate or coerce a civilian population;
(B) to influence the policy of a government by intimidation or coercion; or
(C) to affect the conduct of a government by mass destruction, assassination, kidnapping, or hostage-taking.
So there you go! Now you know what terrorism is, and if you have any questions as to whether, say, bombing a country to change their policies is terrorism, or taking a hostage and firing rockets is terrorism, or writing threats on someone's locker is terrorism, or taking a kid's lunch money is terrorism, all you have to do now is look at the definition, and see if it might apply!
Now, admittedly, this is only US law for the purposes of this executive order--which is terrorist financing--but it is an official working definition of terrorism from the United States--no doubt there are others. However, I would argue that this executive order is quite representative of the US government's thinking and policy on the subject.
However, note that this order doesn't actually apply to all terrorists everywhere--instead, it has a 'list', and the people on that list are considered de-facto terrorist groups, regardless of the above definition. Also added are anyone the Secretary of State says is or might be a terrorist, anyone the Secretary of the Treasury (with approval from others) says is a terrorist or works for terrorists, or financially assists terrorists.
In short, a Muslim in America contributing money to a charity which subsequently gives money to Hamas or Hezbollah could be considered a terrorist--not under the definition, but because Hamas and Hezbollah are both on the list. So, yes, in this case, it is the policy of the United States that it's only terrorism when 'they' do it--we aren't on the list.