The PS4 has been available for 84 months in the US and has sold 34.18 million units. The Switch is currently 11.30 million units behind the lifetime sales of the PS4.
I don't see Switch having any problems outselling PS4 in the US. It already has 2/3 of PS4's total sales and it has a big holiday still coming up and several years of healthy sales left. Switch has this one in the bag.