The quote is talking about an invasion of a nato state not Ukraine.
He only wants to pull the us out of nato because nato is carried by the us and provide nothing. If nato members actually met their obligations he would have no issue remaining. To me that’s a reasonable stance.
Edit: actually its not fair to say trump wants to pull the US out of Nato. Its clear to Nato that the US does not want to leave nato but they(trumps admin) are playing hardball to force Nato members to meet their obligations.