I'm afraid you're rather misinterpreting the map. The Treaty of Westphalia absolutely did not break up the Holy Roman Empire, and the Empire--in fact--would endure up until the 19th century, when it was dissolved by then Emperor Franz II who abdicated the title of Holy Roman Emperor and released all member of the HRE from their obligations to the Empire and Emperor. Franz II had already created a seperate imperial title for himself as "Emperor of Austria", which would of course endure on till the final dissolution of the Habsburg Monarchy in 1918.

It's important to understand that the Holy Roman Empire was not a centralised state as one might see it today. It can be tempting to see the HRE as if it were the United States and each of the constituent Princes as a state, with some degree of power within the system, but ultimately subservient to the central authority. However, this was definitively not the case. The position of Emperor was, in many ways, truly one of a "first amongst equals". This is a bit of a common theme for monarchs in early modern European states as the lack of a central state bureaucracy meant they were ultimately dependent on the cooperation of local officials nominally subservient to them for things like enforcement of laws or collection of taxes. In that respect, what authority the Emperor had over the lands that were contained within the Holy Roman Empire was ultimately limited to what he could get the princes of the Empire to agree to at an Imperial Diet. To that end, the power and authority of the Emperor was heavily tied to their personal holdings, rather than institutional power. While there were Imperial institutions, including a court system designed to handle disputes between the various Imperial estates, these ultimately began to bog down in the lead up to the Thirty Years War. The failure of these imperial institutions was likely one of the major contributing factors to the outbreak and spread of the Thirty Years War. To that extent, the HRE was never a single dominating power that made all decisions on behalf of the smaller entities within it. The Empire was a common set of institutions that provided advantages in terms of protection and support to polities within it, but it's not as if the HRE had a common foreign or domestic policy decided in Vienna or Ravensburg that ended in 1648.

While international relations scholars refer to idea of "Westphalian Sovereignty" the Peace of Westphalia did not necessarily create the idea of territorial inviolability, supremacy of a government in domestic affairs, and the other ideas associated with it. More recent scholarship instead highlights that the Peace of Westphalia was mostly focused on the constitution of the Empire, the rights of Imperial states to choose their own religion (which had previously been established under the Peace of Augsburg in 1555), recognition of Calvinism, as well as granting France and Sweden seats in the Imperial Diet and the position as garuntors of the Imperial constitution. While the idea that Westphalia created the system of modern nation-states is commonplace, and 1648 is usually the starting point for international relations scholars, it's more a convenient start date than anything beyond that. Westphalia was a paradigm shift in that brought an end to the Thirty Years War within the Holy Roman Empire and instituted some Constitutional changes, but it did not dissolve the Empire, or enforce some new paradigm of governance on all of Europe.