Formula 1 also has a national competition element that a US series cannot have - England vs. Italy is a big deal over there - New Jersey vs. Kansas - not so much.....
I agree the two car teams with identical liveries have always been an integral part of F1 (at least in modern times) and it really helps create identities for teams, sponsors and drivers..... I think this is a place where NASCAR is starting to lose it - the different color schemes used for different sponsors on the same car throughout the year seem to fuel die cast sales to hard core fans - but I don't watch Cup racing that much and I just find it confusing and it does not really help me to decide to patronize a sponsor....