Correct me if I'm wrong, but I'm pretty sure the dude is just bluffing. Unless you made a deposit with a debit/card card with a US address, then how would they really know that you're from the US if you're using a non-US IP VPN?
I've been using Binance for a very long time as well, and I never had any issues nor do I know which methods they are using but apparently this is a thing now, and it's being done to a lot of people. I've seen an endless amount of topics (unsolved ones) in /r/Binance.
See here:
https://www.reddit.com/search/?q=Risk%20control