pre 1980's...if americans had to travel more,how different would history be????

this always has interested me
well it is clear that in the 30's,40's and 50 etc

america was clearly the best at boxing and after lets not talk even talk about about countries that could not turn pro

but only about those that could,
like england or germany etc

had joe louis had fought tommy farr in england?
or ray robinson had to rematch turpin in england
what if billy conn had to go to england to fight len harvey
maricano going to cuba to fight vidoz etc

what if european-asian etc fights didnt "have to prove themselves by coming to usa"
what if it was more fair and americans didnt always home court advantage...

were the americans just that much better
or them always playing on home turf have to do with it