Something with discuss in TL-191 was how baseball was so marginalized when predate the POD by years even all 80% of teams were north mason-dixon line but well maybe for that, as rugby-gridiron would be more 'culture neutral'
Still people forgot obvious answer...make it Olympic sports and all european nations play with it, both Football version(Association-Soccer Gridiron-Canadian-American) use similar size game field so can save money making a dual stadium, sold it as a 'strong, tactical team' so central and west europan team would practicez since high school and military service.
Association-Soccer size: Long:: Minimum 100 meters - Máximum 110 meters
Wide: Minimum 64 meters - Máximum 75 meters
America-Canandian-Gridiron
Long:: Minimum 110 meters - Máximum 122 meters
Wide: Minimum 68 meters - Máximum 70 meters
How could the US and Canada convince Europe to put it in the Olympics though? Maybe it continues to grow in Cuba(it had a following there before Castro) and Latin America enough to be serious?