There was certainly foreign collusion in the 2016 election
For starters Christopher Steele is ex-MI6 (British Secret Intelligence Service) and was in contract with some of his former bosses stilll working there during this event. Was it "collusion" when the Clinton Campaign paid millions to this British spy for his fake Russia dossier?
In addition, the Obama administration invoked the cooperation of the GCHQ (Government Communications Headquarters - the British version of the NSA) to skirt US laws to spy on the Trump Campaign. While all of this may have involved a country which is supposed to be our staunchest ally, it still meets the definition of foreign collusion and it is still illegal.
The next is Ukraine where some current politicians there appear to be the original source for the allegations contained in the Steele Dossier which was the sole basis (as far as we know) for the FISA warrants.
See Nellie Ohr: Ukrainian Lawmaker Was Fusion GPS Source
And Victoria Nuland, Alexandra Chalupa, Ukrainian Ties & the Steele...
And, of course, there is Russia --
"Steele cites four different sources – a former senior Russian intelligence figure (who is believed to have been murdered in his car on December 26, 2016), a current senior Russian foreign ministry figure, and two Russian emigres; these sources all indicate that Trump had a relationship with Russian intelligence and was providing information on the comings and goings of Russians at his properties. We know that Trump had a vast surveillance system of his properties, and that President Putin and Russian intelligence keep a close tab on Russian oligarchs.
Dossier - The Moscow Project
And it also appears other European spy agencies were used by the Obama Admin to spy on Trump and his people. And event eh Australians --
"We also have separate press reporting that UK, Dutch, French, German, Estonian, and Australian intelligence agencies picked up intelligence on meetings between Trump associates and Russian intelligence going back to 2015."
You will recall Trump formally announced his candidacy in the Summer of 2015. So, by the time of all of this foreign spying on him, Trump was already running and they all knew it. Thus they were spying on a candidate for President of the United States and reporting what they learned back to Barrack Obama who was the then leader of the opposition party.
So, from my perspective, it looks like there was quite a bit of foreign collusion in the 2016 Presidential Election. And, ultimately, almost all roads lead back to the man who was president at the time.