Hong Kong is a major international financial center. 2 million going from US to Hong Kong is about as remarkable as a snowflake in a blizzard.
As long as your papers are in order and you can provide agreements/invoices if requested, the transfer itself won't stand out.
Mercury wants account holders to have a genuine US presence/connection. If all you're doing is funneling money to HK, they might question the relationship on that basis.