Kind of clever humor, on Trump's part, joking that he and visiting German Chancellor Angela Merkel may have one thing in common: being spied on by Barack Obama’s administration.
In 2013, Merkel was upset that her phone was being tapped by NSA, which isn't really Obama, but he got much of the blame; as in "the buck stops here." The surveillance of our government is a "whipping boy" for both the left and the right. Obama got a lot of flack when he was commander in chief. Now there's some folks, on the left, who are saying that we need to pick our battles better. The government, under Obama, looks pretty good today. Others are suspicious of the government, period.
I don't think Obama was personally ordering spying on Trump Tower, but, in reality, how would I know; from my perch here in Bellingham, Washington?