In my experience, the communication problems stem from the Americans who expect perfect English from all others. English is spoken across the entire business world between people for whom it is not their first language. The accents and broken English is epic in many organizations. Yet they work through it and get things done together.

If you work harder at taking the burden upon yourself to understand others, you might be surprised how well people can learn to communicate despite differing backgrounds.

I have the same experience as you. I have been working with many non-native English speakers from different countries, and Americans (and to some degree Brits) are usually the ones who can't follow what is said. This improves over time as they get used to different accents, but it seems it is easier for non-native speakers to understand foreign accents than native speakers in general.

I'm not saying I always understand 100% of what is said. When someone with an accent from a specific part of a country speaks super fast and is on a poor line with lots of street traffic in the background, it can be hard to follow. But usually I catch enough of it to be able to communicate.

That’s just saying the same thing. American companies have engineering quality loss when they try to collaborate with people they can’t communicate well with. Whether it’s dumb Americans or poor ESL, it’s not really relevant to the outcome because it’s the same.