English-to-French translation...can someone help?

"Lorsque vous êtes arrivé(e) aux Etats-Unis, vous a-t'il été difficile d'acquérir une bonne maîtrise de l'anglais?"

"proficient", when you talk about language, can't be translated by "compétent".

#3 seems closest to me.

Quand vous êtes arrivé aux Etats-Unis (I'm leaving out first here. pour la première fois--for the first time and calling America the US),est-ce que c'était difficile pour vous de devenir compétant en anglais.

'devenir compétant' sounds like 'translation language', English with a French veneer. I think I'd say,

...est-ce qu'il vous était difficile de vous exprimer en anglais? (was it difficult for you to express yourself in English)

...est-ce qu'il vous était difficile de comprendre l'anglais? (was it difficult for you to understand English)

I don't have my dictionnaries with me--perhaps a native speaker will help you out. #3 is really not bad--the only really error is the extra s on arrivé--you only need that if you are adressing more than one person. It's understandable, the others are a little strange.

#1 means When it happened to you the first time in America, was it difficule that did you become competant in English.

#2 means When you arrived firstly (in the first place) it was difficult for you becoming competant in English(but it sounds worse in French.)

French teacher who reads a LOT of babelfish translation from students who think they can get by with it!

First of all, to whom is this addressed? A man? A woman? Someone you know well or not at all? Someone your own age or older? This will make a difference in the translation. For example, the past participle "arrivé" (or "venu" in my translation below) must have an "e" added if you're addressing a woman, an "s" added if you're addressing a multi-gender group or a group of men, and an "es" added if you're addressing a group of women.

However, the third sentence you wrote is closest to correct (although you have written it in the plural form.)

I would translate it thus:

Quand vous êtes venu(e) d'arriver en Amérique, est-ce que vous aviez du mal à perfectionner l'anglais?

OR:

Aviez-vous du mal à améliorer votre niveau de compétence en anglais just après votre arrivée aux Etats-Unis?

If you use your third sentence, I would make the following minor changes (add the "e"s below only if it's addressed to a woman):

Quand vous êtes arrivé(e) en Amérique, est-ce qu'il était difficile (pour vous) au début de devenir compétent(e) en anglais?

None of them is correct. You should normally say: lorsque vous êtes arrivé(s) pour la première fois en Amérique, vous a-t-il été difficile de perfectionner votre anglais?

A votre arrivée aux Etats-Unis, était-il difficile pour vous de maîtriser l'anglais dans la vie courante?

I'd try this because it has the idea of the "early days" ( à votre arrivée), then avoid "Amerique" which is the continent. Go for "les Etats-Unis".

Hope it helps you!

the first one is not right because you have two subjects with 'vous' and 'il'. I would say,

Quand vous etes arrive la premiere fois aux Etats-Unis, est-ce qu'il etait difficle de devenir competent en anglais?

The first on is right!!