KYB for non-US entities onboarding US clients — what's the practical struggle?

We're a non-US fintech trying to onboard US-based businesses, and the KYB process is proving to be a serious bottleneck. Beyond the obvious OFAC/Sanctions checks and beneficial ownership verifications, what are the recurring practical headaches for others? Specifically, are you finding that certain states or business structures (e.g., trusts, complex LLCs) present disproportionate challenges in documentation or verification that third-party vendors often miss or don't streamline effectively? We're trying to figure out if our internal process needs an overhaul or if it's just the nature of the beast dealing with fragmented US corp registries and varied state regulations. It's really slowing down our growth projections.