Just horsefeathers. They conducted mass attacks in up to regimental strength against remote firebases, all the bleeding time. The standard unit of maneuver was the battalion, several hundred men. Most of the troops were NVA regulars, drafted and trained in the north as conventional infantry, and sent south. They also lost these clashes.
They did not defeat the US by wearing us down. We left after building up the ARVN to the point where they could defend the country, after breaking the back of the domestic insurgency (from 1970 on, the VC were a minor force and most was just NVA). When the north tried to take the south conventionally, it was by cross border invasion. And in 1972, with US air power still helping them but US ground troops already withdrawn, that also failed.
The ARVN was not defeated until 1975, years after we left, and that wasn't a rerun of 1972 solely because we had pulled air support for the south. Ford was willing to use US air to help them again, but congress said no. Then a dozen full divisions using nearly 1000 Soviet tanks overran the south in a few weeks, in a campaign just like that of the Germans in Poland in WW II. Guerillas had nothing to do with it at that point.
And the American people never abandoned the war. A majority supported it throughout. The war split the left, with about a third of the country against continued involvement, essentially all of them on the left. This caused a re-alignment, with the left wing capturing the Democratic party and marginalizing it in presidential politics as a direct result.
In 1964 and 1966, both parties supported the war, and the Dems won elections. In 1968, the rioters at the Democratic convention did not, but were fighting the old Democratic party that did, in the streets. The Republicans won as a direct result, as a Democratic president imploded. By 1970, the Dems were against the war but out of power. They ran McGovern in 1972 on the full peacenik platform, and lost in a landslide. The left and the Dems turned against the war, but as soon as they did the American people turned against them.
Nixon's strategy was working and would have continued to work. He tied the supporters of Vietnam in knots, by pitting China and Russia against each other. He mined the harbors and used B-52s on downtown Hanoi when he had to. He unleashed the full weight of US airpower against the 1972 easter offensive and destroyed it, with ARVN providing all the ground component needed. ARVN were not pansies, they were the last to give up, and only lost when the north had massive Russian support and they themselves no longer had any from us. They would have, had Nixon still been in office.
Westmoreland's attrition strategy was not popular and it put high political strain on Washington, to be sure. But militarily, it worked. The North could not support continued infiltration at a high level after losing the mass battles of 65 to 68, because losses had to be dialed down to the rate they could replace. And at that lower rate, ARVN could and did hold. The idea that guerilla warfare is a magical multiplier that always works is a myth. A nation with only a fifth of the manpower of its enemies can't win a war of attrition taking 20 to 1 losses just through higher loss tolerance.
Nam was lost in the Watergate building and in the mismanagement of the coverup that followed. Not in the rice paddies. The left has systematically tried to obscure these historical realities ever since. It wants the war to have been immoral, and hopeless. It wants the NVA to have been fated to win, making it pointless to try and stop them, and exculpating themselves for the eventual defeat of SVN and the resulting murder of a million innocent human beings. It wants the split of the Democratic party in the 60s to have been a split of the whole US, as though hippies were the majority - they weren't.
It wants to pretend McGovern won the battle of public opinion, as though 72-74 never happened, and Nixon was destroyed by the war rather than by Watergate. But the people never abandoned Nixon over the war. They only voted for the left after they thought the war was already over, on Nixon's terms, and that Nixon had then lied to them about domestic politics. The post watergate congressional left then used that ruthlessly to enable their NVN allies to win the war in SVN, because they hated Nixon and everything he had accomplished, and a million dead innocents were nothing compared to their personal power and their invincible sense of self-righteousness.
It is not as pretty a story as "guerillas always win", if you wear Che t-shirts. But it is what actually happened.