All of the above answers - you are definitely able to travel without problem - misdemeanor expungements are no barrier to travel.

Only a VERY few countries (less than the fingers on one hand) have "live" access to our national criminal databases and those very few that do will not care at all about a misdemeanor that was not only dismissed but expunged - and they will not be able to see it, anyway. All other countries have absolutely no possibility of knowing about the arrest.

You can rest assured that you will not be asked the question. In the extremely unlikely event you are asked if you have been arrested what they are really asking is, "Have you ever been convicted of a crime?" to which you should correctly, honestly and truthfully respond, "I have never been convicted of a crime."

You are correct in your anxiety/assumption that expungement might not necessarily mean "there is no record that it ever happened at all."

If you are ever responding to a national security background investigation questionnaire or interview (such as for a USG three-letter agency) and asked if you have ever been arrested then yes, you should definitely answer, "yes, I was arrested but the case was dismissed and the arrest expunged." This is because even though "expunged" the facts are that you have been arrested, fingerprinted and charged, and those facts will be available to those agencies regardless of the "expungement" which was hopefully correctly processed (for example, your fingerprints will still be in the system). The adjudicators of your background investigation will then research the facts and then make a determination if you are a misanthrope or not and unworthy of the position.

But that situation is a FAR cry from being able to travel internationally, as almost all countries have zero to next to zero possibility of knowing about the dismissed and expunged case.

Go! travel freely and often, friend.