Eperience letter in US for H1B workers

Hi Saurabh/ Other experts,

I heard that experience letter from previous employer is not mandatory while switching jobs in US (there are other ways to prove your employment such as: salary slips, timesheet etc ), like the way it is mandatory in India.

Following are my question on this:

  1. Whether above mentioned information is correct or not?

  2. What if I join a company in US and plan to come back to India after 4-5 years, if the company will not provide experience letter that can create problem for me in India?

Can you please give your opinion on this?