Trump said when ask about Syria,Iran,Afghanistan ect. in his fist term that he would not say if he were going to attack by a certain date or where because it would give the terrorist time to move or prepare and would endanger US troops. So I would not take some of the things he says as if it were actually so. He has said since the meeting in Arabia that Putin agreed with putting UN peacekeepers in Ukraine but Russia has denied that they agreed several times. In war misinformation type propaganda has always been seen as a useful tool and so Trump may be saying Putin agreed to it to spread mistrust between the Kremlin and Putin.
The issue of the EU and NATO investing more on defense could possibly be the same that if the US invest in Ukraine then they should also. Money or boots on the ground my make it seem more sensible where if Russia has 600,000 troops in Ukraine then 600,000 or more allied solders are needed to put this in check so 600,000 minus the 30,000 the EU can send leaves the US having to send 570,000 or more troops to Ukraine to make up the difference. Or else there's the other option in regards to Ukraine where France,Germany and the other EU nations issue a draft and we all send the same investment to Ukraine.