I don't think it is the easiest thing in the world to do, but it is definitely not the hardest. Because if you take Donald Trump for example, or any U.S president, they may have already had money, like Trump, yet everyone is not nessisarly aware of who they are exactly, but the fact that they are or were president and people now know who they are because they have moved up in the social class, no, this doesn't happen every day, but, this is just one example. Another one would be in a case where someone won the lottery, nobody really knew who they were before they won, and now they would be moved up in the social class because of their money and fame. So yes, in a sense, social mobility is an easy thing to achieve in the US.
