What does your friend criticise him for? Usually Obama has two types of critics, the republicans who are now trying to rewrite history and pretend that it was Obama who destroyed their economy and democrats who are genuinely disappointed at Obama allowing the machine to curtail him.
I have spent many weeks in the US over the last 6 years and can say that in conversation with American friends and business colleagues they were openly critical of George W Bush and Barak Obama in equal measures.
Like many Brits they have little time for any of their politicians whom they see only as desiring power. I also think there may be the beginning of a serious backlash against the huge sums of money being spent by those seeking election at a time when the average american is suffering economic hardship.
Americans have no compunction about criticising the President within their own country. However, in the past I have always found a reluctance to wash their dirty linen internationally. That is entirely a personal view formed from conversations with American friends.
Others will no doubt have different friends and different views.
In North Korea you dare not criticise the leader even in your own home!