Can americans and british people understand each other with no difficulty?

This has been bugging me lately, I'm brazilian, english is my second language and I don't see that much of a difference between american english and british english. Yes, the accent changes, but not that much that can make it unintelligible to me (Maybe irish english)

BUT I realize this might be different for people who learned english since they were born listening to almost the same accent being spoken at all times.

I'm saying that because even though Brazil's portuguese enad Portugal's portuguese is 99,9% equal when written, I have a lot of trouble trying to understand what portuguese people are speaking. I was taking a class of Portuguese Language History in college and my professor was telling us about a trip she made to Portugal to study a few documents and she could not understand what they were saying to her, and mind you, this is someone with a Doctor's degree in portuguese language. She said that at one time, the guy and her just gave up and they talked in english lol

I also cannot understand a single word of a music if a portuguese person is singing it and I remember that in 2015 I went to watch a portuguese movie at the theater and it was subtitled haha, which was great, because I probably would've lost a lot of the dialogue if it was not.

So is it the same for native english speakers? Do you guys have trouble understanding what people from another country are saying?