It is widespread common knowledge that the American accent is the easiest to understand. If you don’t agree with this, I’m sorry but you are not speaking from experience.
Can you identify any intrinsic property of General American other than media, business and language school familiarity that makes it particularly intelligible? Its pronunciation is as divorced from phonetics as most English dialects, it elides some consonants and vowel clusters that are distinct in most other English variants and it tends to be spoken more rapidly than some English dialects.
And yes, I have considerable experience of speaking English abroad, and whether I think the listener will understand me better if I exaggerate my British diction, adopt more General American-sounding syllables, pick up quirks of pronunciation and phrasing used in the local ESL lingua franca or pronounce a particular problem word as it is written is entirely situational, and generally based on what the person I'm speaking to is most exposed to.
And yes, I have considerable experience of speaking English abroad, and whether I think the listener will understand me better if I exaggerate my British diction, adopt more General American-sounding syllables, pick up quirks of pronunciation and phrasing used in the local ESL lingua franca or pronounce a particular problem word as it is written is entirely situational, and generally based on what the person I'm speaking to is most exposed to.