My American friends didn't vote for Hillers because they wanted Bernie, so they didn't vote at all. I wonder how many did the same, and whether such acts of principle contributed to Trump getting in.
Hillary received 3 million more votes than Trump.
It is likely that your American friends live in either East Coast or West Coast affluent states like California or New York. It would not have mattered how many of them voted for Hillary, since the presidency is not determined by the popular vote.
The presidential Electoral College operates on an all or nothing principle -
all the state votes go to the candidate who secured the most support in that state, so if Hillary received 60% of the votes and Trump 40% of the votes in a particular state and that state has ten Electoral College voters then all ten will vote for Hillary. Trump's victory came from the fact that he secured the Electoral College votes in a large number of small states in which, relative to the overall state population there are more Electoral College places than in the large states.
The inequalities don't stop there: in some states the total state population determines the Electoral College representation, in others it is the results in individual electoral districts. Say that a state has three electoral districts, one with an electorate of 100,000, the second with 40,000 and the third with 30,000. If the two smaller ones each voted for Trump and the large one voted for Hillary, the the state's representation would support Trump.