Considering that those acquisitions proceeded before the intense scrutiny Facebook has received in the past year or two, it is quite likely that it would be blocked.
This is a fantasy. The US government has not meaningfully regulated big tech and there's no reason to believe they will start now (unless you consider the public bloviation of politicians "reason to believe" - I do not).
General regulation for the tech industry and blocking M&A activity from large companies are completely different things. I think it is very fair to assume that the US will block large acquisitions by Facebook, Google, and Amazon going forward.
