I am a candidate from Asia , I have seen in visa cases that they prefer people who have traveled more . Even there in a form in immigration section which asks for how many travels were made by me in past 10 years . I have put 4 countries there , in one case I was invited by a multinational company i.e. Cisco to attend a conference in USA however I was unable to make it due to some commitments here . Do you think putting an invitation letter only would make my immigration case a little stronger ?