building on the great answer from Herbert, I think it's mainly culture.
clients, be it from US or EU, want to be understood beyond the tech requirements (and even these are sometimes difficult to convey to the final developer).
it's a general phenomena: people from different cultures have different constructs about how a company/society should be, beyond the linguistic dimension.
I worked with people from vastly different culture than mine (I'm currently in EU) and it was confirmed to me over and over again that cost for talent for high-quality work is generally the same regardless of geography. In the software-related work at least, I always ended up paying more, either with time or additional funds.

what I can say, assuming you're aiming at high-quality output, is that a portfolio usually sells itself. if you can undeniably prove your authorship of those great past works, I feel half of the work is already done.
on top of that, really understanding the culture around your client, mostly the business/work culture (how things are done, how they communicate, incl. on linkedin, perhaps even who they follow on social media) should fill most of the remaining gaps. this is just my way of saying "learn the business culture"

clarity has a very nice help section (that I've just read half an hour ago), simple and unambiguous.
these 3 in this order helped me:
- https://clarity.fm/help/articles/2/how-does-clarity-work
- https://clarity.fm/help/articles/32/how-do-i-create-a-great-profile
- https://clarity.fm/help/articles/4/are-there-guidelines-or-rules-of-conduct-on-clarity