Decline in U.S. affects India both directly as well as indirectly.
Directly in the sense our services export, of which US is the biggest market, takes a hit. We export handicraft, gems, jewelery, refined oil, textile goods all of that gets effected. Then in these trying times US is take strong position on outsourcing and issuance of work visas for US. that also is bad news for India.
Now, indirectly in the sense that living in a globalised world bring it's own set of advantages and disadvantages . We become part of a global village where chilly wind blowing in one corner brings cold to another. With US going down and the way all major economies are coupled with each other, our trade with each of them is bound to plunge down. ,
But all is not gloom and doom, we have exports as only 22% of our gdp, compare it with almost 40+% of china, we will take hit but still would be in a better state that most of our conterparts.