Question: There are bugs in Canada that bite into the trees & kill them! :( Is there any way you can stop this and help these dying trees?

These types of bugs are not only found in Canada. They are known as invasive-tree killing insects. One example is Aphids which are leaf-feeding bugs are usually not damaging but large populations cause leaf changes and stunting of shoots. Aphids also produce large quantities of a sticky exudate known as honeydew, which often turns black with the growth of a sooty mold fungus. Another example is Gypsy Moths which are one of the “most notorious pests of hardwood trees in the Eastern United States.” Since 1980, the gypsy moth larvae has defoliated close to a million or more forested acres each year. The moth was introduced into the United States in 1862.The insect lays visible buff-colored egg masses as leaves emerge in the spring. These masses hatch into hungry larvae that quickly defoliate hardwoods. Several defoliations can frequently kill trees under stress.
Usually scientist rely on the natural controls instead of killing the bugs. Because these bugs have natural predators in the wild, if we kill tree-eating bugs then we would indirectly kill all the other bugs which are feeding on them and that would affect larger animals that feed on these bugs. As you can see it is like a chain reaction, if we interfere at any step, the whole chain gets affected and that would be a big mistake. However we can introduce a bit tighter controls on these bugs by using less hazardous chemicals.
Thanks for asking such a responsible question. We need people like you who are aware of what is going on around and seek solutions. Thanks lulu