VA's leader insists that work is already underway.
Lawmakers called the scathing report an indictment of systemic problems throughout the department.
But McDonald called it an important recognition of the types of reform he has been implementing for the last year.
"Nobody has wanted to talk about this transformation," he told members of the House Veterans' Affairs Committee. "Everyone wanted to talk about problems of the past."
Those included a nationwide scandal involving VA patient care delays and accountability among department health officials, issues that the report indicates are linked to larger problems of cumbersome bureaucracy and mismanagement throughout VA.
Committee Chairman Rep. Jeff Miller, R-Fla., called the findings a blueprint "to transform the broken VA health care system of today into one that our nation's veterans can finally be proud to call their own."
Rep. Tim Huelskamp, R-Kan., said it showed "a culture of silence" and "a leadership crisis" at the department.
McDonald bristled at those comments but acknowledged leadership has been a lingering weak point for the agency, one he has worked to correct with a host of changes among top department officials and repeated emphasis at all VA offices on customer service and veterans' needs.
He said the most important message in the assessment was its findings of a "misalignment of requirements and resources," requiring more funding and policy flexibility to react to trends within the health care field.
And he said Congress shares the blame for those failures.
"We can't continue making progress without reconciling requirements and resources, and we can't reconcile requirements and resources on our own," McDonald told the committee. "We need your help to do that. Veterans and the American people expect us to work together on their behalf."
Lawmakers did recently approve more funding and flexibility for construction projects, including VA's multibillion-dollar Denver medical complex, which has drawn more criticism of mismanagement and incompetence.
But department officials and Republicans have been sparring over the proposed VA budget for fiscal 2016, which includes $1.6 billion less than President Obama had sought.
McDonald again characterized that as a loss in needed spending power for department programs, while lawmakers charged that their overall budget plan still would mean a net increase for VA.
Both points are largely moot until Congress reaches agreement on a full budget plan. Until then, VA programs will continue to be funded under advance appropriations and continuing resolutions, a situation McDonald called troublesome.
Leo covers Congress, Veterans Affairs and the White House for Military Times. He has covered Washington, D.C. since 2004, focusing on military personnel and veterans policies. His work has earned numerous honors, including a 2009 Polk award, a 2010 National Headliner Award, the IAVA Leadership in Journalism award and the VFW News Media award.