In todays date, United States followed by South Korea,  Japan, India and Singapore have the biggest markets and prospects in fields of Robotics, Artificial Intelligence and Machine Learning Technologies. In Silicon Valley and Bay Area, San Francisco, every day hundreds of startups are being started relating to the above mentioned technologies. On the other hand companies like Tesla, Google and Intel are making huge investments and employments to support the needs of the future. Hence, US is perhaps today the leading country, both in terms of per capita salary (Tech Domains) or in patenting innovative technologies.

Hii!
It depends upon the package you grab. Let me compare and tell you the salary ranges in India and US. In India the salary on an average, of a robotic  engineer ranges from US$ 289.91 US$ 14,495.50 per annum. Whereas in US the average salary ranges from US$ 87,000 US$ 128,500 per annum. The salary also depends on your expertise and experience.
Hope this helps.
Good luck!