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I tried opening a US business account in 18 EMIs, here's the result

I have opened half a dozen Mercury and Relay accounts easily for US companies for non-US owners with addresses outside US in three different industries. The difficulty factor was about the same (quite easy). Between the two, I prefer Relay, though their support can be very slow to respond. I found the response time improves after you have an approved account, however I never tracked response times so this statistic could just be my imagination.
Why you prefer Relay?
 
Mercury has very attractive currency conversion if paid by debit card in other currency than USD. I paid around 0.2% fee. ATM withdrawal in foreign currency should be favorable, but I haven't tested it yet.
 
One of my friends' businesses was rejected by Airwallex, and Mercury closed the account after 1 year (even with US operations).

Not sure why, maybe because US operations were with another non-resident US entity.

All legal, EU citizenship
 
I asked a bunch of EMIs where we didnt have clarity if they would open an account for a US LLC. Here are the responses:

Statrys:
"At Statrys, we primarily onboard companies that are incorporated in Hong Kong, Singapore, or the British Virgin Islands, although there are some exceptions. For your US LLC, we encourage you to submit your application through our website, and our dedicated onboarding team will review your business profile and get back to you with the next steps."

Verifo:
"Please be informed that the US companies with [EU country] UBO are acceptable, but before providing confirmation we need additional information on company’s activities."

Interpolitan:
"Business account: Like above, the business can be registered anywhere that is not sanctioned, other than the US. Unfortunately, due to tax reasons we cannot onboard US entities. If your business had an entity registered elsewhere, we would be able to onboard that."

Narvi:
"We appreciate your interest in opening a business account with us.
Please send an application from the front page of narvi.com.
Our compliance team will review your application and keep you informed."

So only a clear no from Interpolitan. Definitely a possibility for the others (even if Statrys seems a longer shot), depending on citizenship and residency of the owner, and activities and size of the US LLC.