A new, Republican-controlled U.S. Congress convenes on Tuesday eager to repeal major portions of President Barack Obama's healthcare law and roll back environmental and financial industry regulations, but could quickly become embroiled in fights over President-elect Donald Trump's Cabinet choices. Despite his promise to unite a deeply divided country, Trump will be sworn in on Jan. 20 leading a Republican Party that early on will push legislation through Congress without significant - or any - Democratic support. According to a Gallup poll released on Monday, Trump will take office with less than half of Americans confident in his ability to handle an international crisis, use military force wisely or prevent major ethics lapses in his administration. Leading Democrats on Monday warned of a…