Swirbul, 20, raced two seasons with Axel Merckx's U23 program after coming from a mountain biking background, capping off his transition to road by winning the U23 road race national title this year.
In an email conversation with Cyclingnews on Thursday, Swirbul praised his time with Axeon, saying his decision to leave the program was incredibly tough.
Swirbul emphasised that he did not leave Axeon because of any issues he had with the team, rather he is looking at the increased European experience provided by the BMC Development Team, which has an almost exclusively European calendar.
"Basically, after going to Europe for the first time this year, it really dawned on me how different racing is over there," Swirbul said.
"If it all works out in my favour in the next year or two, ideally I will find myself racing on a WorldTour team in Europe. I would much rather go over and experience racing in Europe full-time when I am in under 23, when perhaps there is less pressure to perform, than go over having just signed a contract with a big team and struggle with the different racing style and different culture."
Swirbul said that after looking back at the 2015 results, he noticed that most of the riders who were doing consistently well in Europe this year all scored contracts this fall with WorldTour teams.
"There were a handful of riders racing in America who, quite frankly, dominated the scene and in my opinion were 100 percent deserving and strong enough to race in the WorldTour next year but did not receive a contract," he said.
"Had they been racing in Europe, perhaps they would have won a ton of races or been up there in the results and who knows, maybe they'd be riding for Sky next year? So for me, once the opportunity to go full time in Europe came to me, my gut was telling me that I have to be over there to learn, even though my heart wanted to stay with Axeon."
Swirbul, a talented climber, also said that the races he'll target in Europe next year are better suited to his skills than the races Axeon targets in the US, such as the Tour of Utah and the USA Pro Challenge.
"I will also get plenty of opportunity to do races that are not my specialty, where I will be forced to learn the skills I lack currently," he added.
BMC Development Team rider Alexey Vermeulen, 20, recently signed a two-year WorldTour deal with LottoNL-Jumbo, but Swirbul said that news did not affect his decision, as he had already inked a deal with his new team.
"..(But) it did reinforce my thinking that I had made the correct decision with BMC," he said.
The program Swirbul will race next year has not been decided yet, but he said he believes he'll start in Belgium and France with some hilly races before returning to the US for the National Championships. His focus will then likely turn to the mountainous races in Europe throughout the summer.
"My goals are simply to learn as much as I can," he said. "I don't really have any specific result I'm looking for, but, despite my terrible showing in my one European race this year, I know races like Giro Valle d Aosta, Avenir and spring races like Ronde Isard and Pays Savoie are perfect for me, and I'd like to do well there if they are on my program."
Before changing his focus to next season, Swirbul, who recently broke his wrist in a mountain biking crash, paused to thank Merckx and his development program one last time.
"When I went to training camp in spring of 2014, I had absolutely no idea what to expect," he said. "At that camp I was so terrible. I must have crossed wheels with a rider in front of me and crashed five times throughout the week, haha! But Axel still put me in races and I slowly began to learn. I really do owe everything I have done in the sport in the last two years to that team and Axel Merckx."