To,
American Consulate General
<Address of the consulate>

From,

<Your Address>

Dear Sir/Madam,

Re: Request for Visitor's visa to the United States

I, <parent's name>, would like to request you to please grant me Visitor's Visa to visit the United States of America during <time frame of their visit, like this fall or this spring or this summer etc>. I would definitely come back to India within the allowed timeframe for the following reasons <Bullet point your reasons and high light any main reasons you might have here>

1.
2.
3.
....
.....
.......

Once again, I would like to humbly request you to consider my application and grant me visitor's visa.

Sincerely,
<Signature>
(Name of your parent)