Buddy, you need to rebuild your self confidence first.
You are scared now.
There are a lot of idiots in U.S., but their English is very good.
Believe me your IQ is far higher than theirs.
Your hardware is good enough to crack any English exam, only if you want, you dare and you really want to make it.
Rule NO.1, tell yourself "I can make it", from the bottom of your heart.
It is a truth, you need the courage to keep going.
Secondly, you need a plan, a realistic and reasonable plan.
What's your work load for your graduate program application?
How many courses you need to be fully prepared?
How many books of practice must be covered?
How many times?
What's your daily load?
How much time in your control?
When to get up?
When to go to bed? etc.
Rule NO.2,
Don't keep saying "I want this, I want that".
All you need to do is very simple, a reliable plan, and
follow it rigidly and firmly, never stop until you make through all the exams and procedures and finally get there.
Every year, tremendous of ambitious fellows make it, tell yourself, "I can make it too."
In my eyes, persistence is the solo secret of life.
I wish you all the best my friend.
Waiting for your good news.