Of course, we should probably evacuate North America before trying something like that.
2. Yes
Roughly 74,000 years ago, a "super-eruption" took place in Indonesia, the largest know eruption in the past 100,000 years. The Toba eruption was enormous, throwing out roughly 1000 times as much rock as the 1980 eruption of Mt. St. Helens (Fig. 1). Dust trapped in polar ice cores shows that ejected material spread around the globe, indicating that the eruption injected substantial material into the stratosphere, where it can strongly affect climate. How much and for how long the Toba eruption actually affected climate and life on the Earth's surface has been the subject of intense debate.
If volcanic activity were to increase, the effect would depend on what kind of increase. Volcanoes do produce CO2, and more CO2 would of course worsen climate change. But they can also produce SO2, which cools the climate rather than warms it. Unlike CO2, SO2 degrades, so the effect isn't as long-lasting.
Volcanoes can also put particulates into the air which block sunlight. Again, the effect is temporary, as the particles fall out. So it would take a permanent, ongoing change in volcanism to counter warming. It would also cause a lot of other climate changes, which are hard to predict.