Interesting what you say about a 100 year war
started c. 1917.
Do you mean America has been at war or the whole world?
both, more or less.
i see america as the heir to the old british empire,
and as america 'grew up' and began to assume it's role
it found itself finishing the job that the british began,
i.e. uniting the key areas of the earth,
vital resources, lines of commerce and communication,
under a single authority.
and really, one could even see that process
as just a secondary stage to an even earlier
global conflict which our history books refer to
as the age of colonialism or the age of empires.
the world's primary economic engines,
the 'CORE' of civilization/industry/commerce
have been waging more or less
constant war upon the less developed parts of earth
for about 500 years now.
the colonization of america itself
was also a part of the process,
and in it we can clearly see the
threat and intention of 'civilization'
to subdue and assimilate 'wild tribes'
into their sphere of control.
this process has largely been completed
in most areas of earth with one notable exception-
a band of under-developed 'nations'
in the earth's tropics/subtropics
that spans the earth on both sides
of the equator.