Is btech Electronics and communication engineering degree is eligible for Masters in computer science in USA
Yes, definitely! See according to the system of most of the reputed US colleges (including Ivy League), all the circuital branches such as Computer Science, Electrical Engineering, Electronics and Communication Engineering etc come under one department of EECS or Electrical Engineering and Computer Science, so if you have done you B.Tech in Electronics and Communication Engineering, then you can definitely apply for MS or PhD in Computer Science in US colleges without any difficulty if you score well in GRE and other exams.
Hope I have answered your question. All the best!