Does the existence of other visas in the passport provide us to get USA visa more easily?
Yes but no consulate mentions about this. Of course it has effects on this.
For example, if you have a schengen visa in your passport, the consulate will think that you are such a trusting person that you could have schengen visa.
For those who have received visas from other countries will be even easier to take visa from United States of America.
Despite this, the American government has a number of procedures. This process than any other country can be even more challenging to have a visa.
This is a positive thing for you. You could take more easily USA visa from the others.
Good luck to you for taking visa from USA.