Indirect pronouns2
A EE.UU. no le conviene actuar sin el apoyo de la ONU
Why does that le have to be there?
2 Answers
It's easier to understand when you ask this question in the reverse: Why do "a ella" or "a él" follow the indirect object "le"?
In both languages, indirect objects answer "To whom?" or "For whom?" questions. English requires that you express the answer in only ONE of the two ways, for example:
To whom did you mail the letter?
I mailed the letter to her, OR I mailed her the letter.
You cannot use both at the same time in English. However, in Spanish, you can use both for emphasis. These are formed as a una persona. This is most common with things like:
A mí me gusta viajar. Ya te dije eso a tí.
One problem with Spanish and other Romance languages is that while they place so much emphasis on gender (maestro y maestra), the third person singular (sometimes plural, too!) can be a little ambiguous! This is the root of the problem you have brought up.
So, think of all these concepts together now. You know you need an object (to me, to you, to him, to her, to us, to you all, to them) to answer these questions. You know how they are formed (me, te, le, nos, os, les). But your problem is that you don't know who we're talking about specifically when you simply say to singular third person! You must then realize that le is the only way to answer your question of "To whom?" or "For whom?" in Spanish, but specifying with a ella or a él is a way of specifying the actual recipient of this indirect action.
As a general rule: The indirect object is always necessary. The emphasis is not.
Do you understand the rest of the sentence ahernandez?
Without the le it shouldn't be easily understood.
To maybe clear up something that Hseminati didn't flat out say, A EEUU is the signifier that tells you there is an indirect object. Convenir is, in this case, another one of those verbs like Gustar that people mentioned in the last post you made.
Just because I felt like it, I went to a reference article here on the site about Gustar and verbs like it. It lists convenir as "to be better for."
In this sentence it means it would not be suitable for the United States to act.