Let's not be disparaging about Rugby in the USA.
The 'Rugby World Cup' was first held in 1987, and won by New Zealand.
Prior to that the only true world competition in Rugby was when it was part of the Olympics. The last Olympics to feature Rugby were in 1924, when USA won Gold.
This means that USA were Rugby world champions for 63 years.

It is unlikely that any other country will ever match that record.