You might be looking at this within the context of the reformist/conservative Right, which (in the United States, at least, and I imagine most nations in Western Europe) is the most prevalent tendency of the Right if my perspective isn't completely skewed.
Since it's relatively easy for reformist groups to work together (compared to radical groups), as they all work through more or less the same politically- and socially-"legitimate" methods, it might seem that they're more capable of banding together and accomplishing their goals compared to the left. But I don't know whether that's necessarily true.
There are squabbles and internal conflicts even within the relatively small movement of radical white supremacists - Christians against neo-pagans, patriotic groups against revolutionary groups, reformist ultra-conservatives against militant neo-Nazis. Then you get into all the divisions along the spectrum of the Right, which can be as complicated as the divisions in the Left.
Hell, it's possible that Left groups (and groups that consider themselves apart from or beyond the Left but still associate with them on occasion) are just as capable as the Right when it comes to forming coalitions or temporary alliances around certain subjects - for instance, immigration.
Beyond those coalitions based around broad subjects, I'm not sure alliances on the Left are actually possible or desirable? Can anarchists work with authoritarian socialists? Can revolutionary leftists work with reformist liberals? It might be possible within certain contexts, but it's obvious that these groups don't have the same goals nor methods in mind.