From the above Fig. 2 it is clear that NYT is now, and for some time has been, reporting noticeably more cases nationally compared to either COVID Tracking Project or USAFacts. The absolute difference in reported cases between NYT and COVID Tracking Project, as well as that between NYT and USAFacts, has also been increasing for most of the past two months (i.e. all of April and May) Another pattern that has been ongoing for some time now is that NYT is reporting more cases than JHU, and the difference between these two has also generally been increasing over the past two months. Nevertheless, it is noteworthy that JHU is reporting more cases than either COVID Tracking Project or JHU, and that, again, both the gap between JHU and COVID Tracking Project and the gap between USAFacts have been steadily increasing for most of the last two months. Finally, COVID Tracking Project and USAFacts have been reporting the most similar numbers of nationwide cases of any two trackers included here, as is evident from the differences line for COVID Tracking Project-USAFacts in Fig. 2 having mostly fluctuated closer to the x-axis than any of the other five.

COVID Tracking Project vs. JHU

During all of March and the first few days of April, COVID Tracking Project reported more cases nationwide than did JHU. (Note that all subsequent figures refer to national data unless indicated otherwise.) However, on April 5, this changed and JHU's case count surpassed that of COVID Tracking Project. This has remained the case ever since, so that as of May 31, JHU was reporting 6,602 more cases nationally than COVID Tracking Project. 
The Pearson correlation between the number of cases reported by COVID Tracking Project and JHU was 0.9999971.

COVID Tracking Project vs. NYT

On March 3, 2020, COVID Tracking Project was reporting just 1 more case than NYT. COVID Tracking Project's lead over NYT then grew until it reached its peak of 4,643 cases on March 23, at which point it started shrinking. By April 2, this lead had been completely eliminated and NYT was now on top, reporting 467 more cases than COVID Tracking Project. Since then, the NYT's lead over COVID Tracking Project has grown to 15,194 cases (as of May 31).
The Pearson correlation between the number of cases reported by COVID Tracking Project and NYT was 0.9999970.

COVID Tracking Project vs. USAFacts

From January 24 to February 29 inclusive, USAFacts was reporting more cases nationally than COVID Tracking Project. But this changed on March 1, when COVID Tracking Project reported a total of 4 more cases than USAFacts. This was the first time that COVID Tracking Project reported more cases than USAFacts, a pattern which continued until April 3, when the number of USAFacts cases surpassed the number reported by COVID Tracking Project by 1,017 (by contrast, the day before, April 2, COVID Tracking Project was reporting 2,291 more cases than USAFacts). Since then, these two trackers have exchanged positions relative to one another ten times (as of May 31).
The Pearson correlation between the number of cases reported by COVID Tracking Project and USAFacts was 0.9999970.

NYT vs. USAFacts

Every day from March 26 to May 31 inclusive, NYT has reported more cases than USAFacts. On March 26, NYT reported 495 more cases than USAFacts, and by May 31, this lead had grown to 19,736 cases. 
The Pearson correlation between the number of cases reported by NYT and USAFacts was 0.9999990.

NYT vs. JHU

Every day from March 25 to May 31 inclusive, NYT reported more cases than JHU. During this time, the lead NYT's case count has over that of JHU has grown from 2,686 on March 25 to 8,592 on May 31.
The Pearson correlation between the number of cases reported by NYT and JHU was 0.9999996.

USAFacts vs. JHU

Every day from April 5 to May 31 inclusive, JHU has reported more cases nationally compared to USAFacts. On April 5, JHU reported 1,690 more cases nationally than did USAFacts, and this value grew to 6,602 more than USAFacts by May 31.
The Pearson correlation between the number of cases reported by USAFacts and JHU was 0.9999987.

Comparing the number of deaths across the four trackers

Fig. 3 below shows the total number of COVID-19 deaths in the United States reported by the four trackers. As is evident from this figure, COVID Tracking Project (blue line) has reported significantly fewer deaths than any of the other three trackers (orange, gray, and yellow) for some time. The other three trackers' death counts have tended to cluster more closely together.