Perhaps the American revolution isn't as obvious a case because the Brits tended to turtle a lot; not trying to demonstrate that they were in control of nearly the whole place and so providing a plethora of targets (unlike the Japanese, say.)
But I haven't asserted that all regular wars have front lines all the time. Just that guerrilla wars don't.
Not true. Show me where in "On Guerrilla Warfare" Zedong - an expert on the American and French Revolutions - claims that guerrilla warfare requires external support.
Guerrilla warfare requires the support of the population (pretty much all US IW joint doctrine highlights this).
Economic power facilitates guerrilla warfare, along with the transition to traditional warfare, but it isn't a requirement.
> Washington had to keep British costs high while not losing, he couldn't just sit.
The only thing Washington had to do was survive.
The KMT was also a revolutionary force (against foreign domination), and initially preferred by Moscow for practical reasons - the USSR would at that time only support a joint command.
Mao became leader of the Reds because USSR's contact defected to Mao from the previous general so the money etc had to go to Mao, the only point of contact the USSR then had with the Reds.
Post WWII Soviet support, esp military material support became very large indeed, allowing the Reds to crush the KMT.
Mao spent plenty of time and effort downplaying everything the USSR had done for him and in massive spats with the USSR, for his own political reasons. Just as Lenin didn't credit the massive support the Germans had given him, to undermine the Czar.
Washington had to keep British costs high while not losing, he couldn't just sit.
Mass conscription is difficult if you can't pay or properly feed or clothe the army you have and a big portion of your own population opposed to you.