If the US government is covering up anything, it's incredible incompetence. Most of that incompetence has now been fully exposed by multiple whistleblowers and investigations - ignoring multiple warnings, poor security check procedures etc.
If the "very suspicious" feeling you're referring to pertains to actual involvement of the government, I'm afraid that's venturing into cloud cuckoo land - whether that's a Pakistani, Mexican, Indian or indeed an American.
I fully agree that we can't believe the White House or indeed any national government on everything. However, we can trust them to be utterly useless at maintaining long term coverups. In today's world, almost everything gets exposed. Lies like the WMDs in Iraq come out in politically driven investigations, books, podcasts etc. etc. Incompetency and a tendency to gloat is our best defense against the supposed secret cabal that's controlling the world.