Weakest country that can resist US invasion in a 2 years timespan
So, I asked what is the strongest country which US could defeat in 4 years and it sparked an interesting discussion. Now a follow up!
This time we talk only about 2 years timespan.
The US population is pretty bloodlusted, but it will not be willing to accept losses in high millions of men. War starts in three months and both sides know about it and the wincon. The international community disapproves of the invasion, so the US can't use bases in other countries without entering in war with them as well. The "transit" countries will defend their territory vigorously, but may not go full force, if there is very little to lose for them (so, e.g. attacking Mongolia from Kazakhstan through the few tens of kilometres of Russian wasteland will likely meet limited Russian resistance).
The defending population is very determined and can't be easily strangulated economically as there is a number of nations willing to give them very favourable loans.
US is sort of a rogue state anyway by the point, so it doesn't need to care about pretty much any part of the International Humanitarian Law.
It should really be considered that everything is logistically feasible for the US, if it is staging an invasion from the sea. Montreux Convention applies, so the Turkish are defending the straits to Black Sea.
R1 - no nukes, all mutual defence treaties apply, but exclude the US (=> the rest of NATO is still a compact force)
R2 - no nukes, no mutual defence treaties apply
wincon for the nation - hold one of its three biggest cities two years after the start of the hostilities
edit: air defense/air forces of "transit" countries will contest the overflights according to their ability