A few days ago HALs stock pops on insider rumours that the deal is likely to close. The planted story was to beat negative stories of the merger in the press.
http://www.reuters.com/article/us-baker-hughes-halliburton-idUSKBN0TS2I820151209
The negative stories are entering the media just now.
http://www.wsj.com/articles/finish-line-is-still-distant-for-halliburton-baker-hughes-deal-1449794130
The problem is not the American market, the problem is smaller markets wherby the service provider sells a package of services. Where Ma and Pa competitors aren't in the market.
The U.S. government is facing political pressure to veto mergers in general.
http://www.economist.com/news/business/21679810-frenzy-deals-awakening-americas-antitrust-regulators-pushing-limits
Brazil is the only jurisdiction facing political pressure to veto this particular merger. Petrobras is state owned, and has been plagued by scandals from service contracts and bribes.
http://seekingalpha.com/article/3740516-brazil-looks-askance-on-the-halliburton-baker-hughes-merger
The DOJ will save face and veto the merger if a foreign country will veto the merger. Take for example the Staples and Office Depot merger, was only vetoed by the DOJ because Canada was about to the same thing. It needed to veto the deal before Canada stopped the merger.
http://www.bloomberg.com/news/articles/2015-12-08/u-s-asks-court-to-block-staples-merger-with-office-depot
I will conclude this, if the DOJ approves the merger, it will knowing Australia, China & Brazil will approve the merger. Otherwise it will veto the merger.
The US can not have a foreign government veto the merger (with exception of the EU), it would make them look weak.