There's no reasonable debate about whether the US has the capability to capture Greenland. Obviously they do. It's in their backyard in an area the US military has been patrolling for decades, with (admittedly decrepit) US bases already present.
The question is whether the US is willing to pay the costs to do so. Sending European troops is attempting to raise the costs of invasion so that any rational actor would decide against it. Of course, we wouldn't be in this situation if all the parties involved were rational actors.
The question is whether the US is willing to pay the costs to do so. Sending European troops is attempting to raise the costs of invasion so that any rational actor would decide against it. Of course, we wouldn't be in this situation if all the parties involved were rational actors.