A great deal is known about individual-level phenomena that harm the quality of engagement in the public sphere, such as perceptions of exposure to disinformation, actual exposure to false content, sharing of false news stories online, distrust towards the news media, news literacy, or individual perception of news quality and credibility. Some studies also consider those concepts and their incidence at the system-level. However, this literature remains highly US-centric and has tended to treat these concepts separately: as studies of news, or of social media, or of disinformation, or of trust in information. What connects these phenomena is epistemic in nature. With recent scholarship showing epistemic threats arise in the absence of outright falsehoods, the need for a more encompassing framework becomes ever more pressing. This dissertation integrates the literature on these epistemic problems by treating the problem of disinformation, distrust in the media and feelings of disorientation as distinct dimensions of a single, broader concept: epistemic vulnerability. This concept more accurately capture the broader phenomenon of the eroding authority and value traditionally attributed to political information. This dissertation investigates this novel construct, epistemic vulnerability, from two angles: the global trend towards more hyperpartisan media, and system-level vulnerability. I ask the following questions. How can we differentiate hyper-partisan news outlets that contribute to epistemic vulnerability from moderately partisan or responsible “mainstream” news? How do levels of epistemic vulnerability vary across Western democracies? What is the relationship between the structure of political and media systems and levels of epistemic vulnerability? Chapter 2 introduces a new approach for identifying channels that contribute to making news environments more epistemically vulnerable in national contexts outside the US. Using data from the ReCitCom survey project (wave 2022), I propose audience-level metrics that can detect abnormally partisan news audiences cross-nationally, relying on two indicators: ideological lean and bias in voting behavior. I test this approach on the French media ecosystem and find that the audience of CNEWS, a major 24/7 news channel, is much more ideologically radical compared to other French news audience. I also find that it is disproportionately supportive of the far right in national elections. Comparatively, CNEWS and Fox News are equivalent in terms of ideological lean, and the voting bias in favor of the far right is actually more pronounced in the case of CNEWS. In conjunction with its track record of violating French media rules, these indicators suggest that CNEWS engages in problematic behavior analogous to Fox News in the United States. Chapter 3 integrates the literature on epistemic problems and builds the theoretical framework for epistemic vulnerability and articulates the relationship between disinformation, feelings of disorientation and distrust towards the professional news media. Chapter 4 presents the Epistemic Vulnerability (EV) Index, a tool for quantifying the health of news environments in a comparative manner. The study employs Ordinary Least Squares (OLS) regression models to explore the relationship between epistemic vulnerability and various structural characteristics of political and media systems. The results indicate that Northern European countries demonstrate higher epistemic resilience, while the United States, Spain, and Eastern European countries exhibit greater vulnerability. The study confirms the significant role of factors such as populism, ideological polarization, political parallelism, public media viewership, and the size of party systems in influencing epistemic resilience or vulnerability. Chapter 5 reflects on the findings and their implications for future research and policy. It critiques the "Pulitzer Prize Syndrome" in journalism research, emphasizing the importance of considering variations in national contexts and the impact of public broadcasting and media regulations.