How are you defining far right and far left for that question, PTTG?
I think the obvious answer being looked for is "the far right wants to genocide all minorities and the far left just wants to create a classless utopia" or something along those lines, but that's not really realistic. While there certainly are outright Nazis in the country, the amount of, well, anything that they actually represent is continually played up for the purposes of being an excuse; it definitely makes it easier to make whatever point someone wants to make when they go "WELL YOU GUYS ARE/HAVE NAZIS" no matter how insignificant a portion these people really are. By far the majority of the alt-right isn't Nazi -- it is often at least somewhat racist, and can be anti-semitic, but you're going to find very, very few people with any sort of policy goals to actually commit genocide.
It's great optics to act like neo-Nazis dominate the far right (both for the Nazis AND for the left) and so of course people act to magnify that impression wherever possible, but it doesn't really fit reality.
Of course, the response that would immediately come to mind if I were to be arguing from much of the left's position is that neo-Nazis have committed some atrocious acts of violence (which is true) and that therefore the Nazis are a significant force in politics -- but a connection I rarely see being made is that this is the same kind of logic that the right has brought to bear against Islam for many years. Somebody on the farthest, smallest fringes of something committed violence, therefore the general sector of ideology or religion they come from must be full of genocidal maniacs who want everyone who isn't them dead, the logic goes, and it's not any more true for the American far right than it is for Islam -- but just as many on the right found it politically convenient to make it seem like Islam is dominated by radical terrorists, much of the left now finds a golden opportunity to pretend like the far right is literal Nazis and is overwhelmingly genocidal.
This isn't even to make it easier to dismiss people on the far right, I suspect, but rather used as a golden opportunity to hit anyone more center-right with because it's good for shocking people and shutting them up -- it's pretty hard to respond to being called a Nazi or Nazi sympathizer simply because it's much more of a grave and shocking accusation to receive than it is to give. Instead I'll present a more in-depth and cogent exploration of the far left and far right than I suspect you were expecting anybody to actually give, though it's not going to be as long as this whole bit because now that I've written all of this I'm starting to run out of steam.
Alt-right is a very nebulous label and the nature of the American far right in general reflects this -- you've got a kind of common sector forming but what people on the alt or far right actually believe varies quite a bit. Some people want to make the United States extremely insular and oppose immigration, some people want to counter social trends (iiiincluding civil rights) and some people want to establish a white identity for the United States. I don't think that all of these people are racist, I can buy there being other motivators for some of the people out for insularity, but I think that a very, very large portion of the far right is racist and/or homophobic and/or sexist. Exactly what that portion is depends on where you actually define the far right to be.
As for the far left... I don't really think that America has a meaningful far left because what you really see are splinters that sometimes intersect but which do not form a united whole.
One splinter is the, and I hate using this term, archetypal "social justice warrior". Maybe it's just better defined as the far left on social issues. You have people who are racist, sexist, and otherwise bigoted but simply pointing the other way, but also people who simply take an aspect of the left's social issues, take it to a relative extreme, and hold it as the highest priority -- I'm never sure how big this splinter of the far left actually is, and I suppose that it really also comes down to how I define who's actually "far left" in this group.
Another splinter is that of communists or revolutionary socialists, who desire the overthrow of society or at least its radical reform into one based on the Marxist ideal (and sometimes the Marxist dialectic, if they're full communist). This, let's be blunt, is a very very small portion of the left and though it's enough to at least get someone like Kshama Sawant into office, I don't think it's very significant in the United States.
Another splinter is that of people who... just want to hit people. I think that there's a third splinter of the far left that really has no policy plans at all and instead simply wants to go out and beat people up. This splinter is smaller than people on the right like to portray it to be, but considering that I see this group of people often outright defended in a way that noone ever actually defends the Nazis, I'm not sure how small it actually is.